Low-halogen compounded flame retardant for non-combustible cotton and preparation method thereof

Abstract

The application provides a low-halogen compound flame retardant for non-combustible cotton dripping and a preparation method thereof, and belongs to the technical field of flame retardation; the preparation method comprises modification coating of aluminum hypophosphite, preparation of a composite powder, silane modification of aluminum hydroxide and mixing; the preparation of the composite powder comprises adding zinc oxide and cerium oxide into deionized water, uniformly stirring, adding polyethylene glycol 400 and hexamethylenetetramine, ultrasonic dispersion for 30-35 min, temperature rising to 60-63 DEG C, adding sodium hydroxide solution to control the pH value to be 10.0-10.5, transferring to a hydrothermal reaction kettle, temperature rising to 145-155 DEG C, and heat preservation reaction for 3-4 h to obtain the composite powder; the flame retardant has good flame retardation effect, high mechanical strength and excellent stability.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant technology, specifically relating to a low-halogen compound flame retardant for dripping non-combustible cotton and its preparation method. Background Technology

[0002] Polyolefin materials such as polyethylene (PE) and polypropylene (PP) are widely used in construction, electronics, automobile manufacturing, packaging and other fields due to their lightweight, chemical resistance, excellent processing performance and low cost. However, polyolefin materials are flammable, with a limiting oxygen index usually below 20%. They are prone to producing molten droplets when burning and the flame spreads rapidly, which can easily cause fires. Therefore, flame retardant treatment of polyolefin materials is crucial.

[0003] With increasingly stringent environmental regulations, traditional halogenated flame retardants are facing growing restrictions due to the release of large amounts of toxic and harmful gases and corrosive fumes during combustion, posing serious threats to the environment and human health. Low-halogen compound flame retardants, as alternatives to halogenated flame retardants, balance flame retardancy with environmental requirements, and have become a research hotspot in the field of polyolefin flame retardant modification. Low-halogen compound flame retardants typically use inorganic flame retardants as the main component and organic flame retardants as auxiliary components, utilizing the synergistic effect between the components to reduce halogen content while ensuring good flame retardant and mechanical properties.

[0004] Currently, the preparation methods for low-halogen compound flame retardants in existing technologies mainly fall into the following categories: First, select inorganic flame retardant components such as aluminum hypophosphite, aluminum hydroxide, and zinc borate, and combine them with a small amount of organic flame retardant (such as melamine polyphosphate and 2,3-dimethyl-2,3-diphenylbutane). Then add appropriate amounts of antioxidants, lubricants, and other auxiliary reagents, and mix them evenly at room temperature or low temperature. This method does not require surface modification of the flame-retardant components, is simple in process and low in cost, and is currently the most widely used preparation method in industry.

[0005] The second method is the simple coating modification-mixing method. Specifically, a single inorganic flame retardant component (mostly aluminum hypophosphite or aluminum hydroxide) is selected and simply coated with melamine-formaldehyde resin or a single silane coupling agent. After modification, it is mixed with other unmodified inorganic flame retardant components, organic flame retardants and auxiliary reagents, and after stirring and drying, a low-halogen compound flame retardant is obtained.

[0006] However, the above two methods have the following drawbacks: 1. Inorganic flame retardant components have poor dispersibility and poor compatibility with polyolefin matrix; the polarity difference between inorganic components and polyolefin matrix is ​​significant, and inorganic flame retardant components are prone to agglomeration in polyolefin matrix and cannot be uniformly dispersed. This will not only reduce the flame retardant effect of flame retardant, but also reduce the mechanical properties of composite materials, resulting in brittleness and a significant decrease in impact strength and tensile strength.

[0007] 2. Weak flame retardant synergistic effect and unstable flame retardant performance; most low-halogen compound flame retardants in the existing technology are simple mixtures and have not formed a complete synergistic system; on the one hand, aluminum hypophosphite cannot be efficiently coated and modified, and it is easy to decompose and migrate at high temperature, and cannot continuously exert flame retardant performance; on the other hand, zinc oxide and cerium oxide are mostly physically mixed, and cannot give full play to their synergistic effects of catalytic char formation, free radical capture and smoke suppression, resulting in a low limiting oxygen index of flame retardants, making it difficult to achieve V-0 vertical burning rating, and failing to meet the application requirements of "dripping non-combustible"; 3. Poor aging resistance: In the existing technology, zinc oxide and cerium oxide have not undergone hydrothermal composite treatment, resulting in large and unevenly dispersed particles. Under long-term high-temperature conditions, they will further agglomerate, becoming the starting point of material cracks. This leads to a low mechanical property retention rate of polyolefin composite materials after high-temperature aging, which cannot meet the requirements for long-term use. 4. Large addition amount: Low-halogen compound flame retardants prepared by existing technology cannot fully exert their flame retardant performance when the addition amount is small; when the addition amount in polyolefins is large, although it can enhance the flame retardant performance, it will also reduce the mechanical properties of the composite material and change the color of the matrix. It cannot achieve the ideal effect in transparent materials.

[0008] Therefore, a low-halogen compound flame retardant for dripping non-flammable cotton and its preparation method are provided. This method is environmentally friendly and can overcome the contradiction between flame retardant performance and mechanical properties at low addition levels. It also ensures that the cotton will drip but not ignite during flame retardant testing.

[0009] To address the technical problems existing in the prior art, this invention provides a low-halogen compound flame retardant for dripping non-flammable cotton and its preparation method, which ensures mechanical and flame retardant properties while maintaining low addition amount, enhances environmental friendliness, and improves thermal stability.

[0010] To address the aforementioned technical problems, the present invention adopts the following technical solution: A method for preparing a low-halogen compound flame retardant for dripping non-flammable cotton includes the following steps: modification and coating with aluminum hypophosphite, preparation of composite powder, silane-modified aluminum hydroxide, and mixing. The specific operations are as follows: 1. Modified coating of aluminum hypophosphite First, add anhydrous ethanol to a three-necked flask and stir at 300-400 rpm. Heat to 40-45°C, add aluminum hypophosphite, and continue stirring for 30-35 minutes. Add the compound modifier in 3-4 portions, with an interval of 4-5 minutes between each addition. After the addition is complete, keep warm and stir for 55-60 minutes. Increase the speed to 500-600 rpm and raise the temperature to 60-65°C at a rate of 2.0-2.5°C / min. Stir and reflux for 2-3 hours. After filtration, dry at a vacuum of -0.08 to -0.09 MPa and 80-90°C for 8-10 hours to obtain modified aluminum hypophosphite. The volume-to-mass ratio of the anhydrous ethanol, aluminum hypophosphite, and compound modifier is 500mL:1000g:50-80g. The preparation method of the compound modifier is as follows: melamine and 35-37 wt% formaldehyde solution are mixed, amino-terminated polyether is added under stirring, and after stirring evenly, 5-8 wt% sodium hydroxide solution is added to adjust the pH to 7-9 to obtain the compound modifier. The terminal amino polyether has a molecular weight of 230, a total amine value of 8.1-8.7 meq / g, a primary amine content of 97-98%, and a viscosity of 9.2-9.8 cSt at 25°C. The mass ratio of melamine, formaldehyde solution, and amino-terminated polyether is 30-50:40-50:0.5-1.5.

[0011] 2. Preparation of composite powder Zinc oxide and cerium oxide were added to deionized water and stirred until homogeneous. Then, polyethylene glycol 400 and hexamethylenetetramine were added and ultrasonically dispersed for 30-35 minutes at a power of 300-320 W and a frequency of 38-40 kHz. After ultrasonic dispersion, the temperature was raised to 60-63℃, and 4-5 wt% sodium hydroxide solution was added at a rate of 2-3 mL / min. The pH value was controlled at 10.0-10.5. The mixture was then transferred to a hydrothermal reactor, and the temperature was raised to 145-155℃ at a rate of 2.0-2.5℃ / min. The reaction was maintained at this temperature for 3-4 hours. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. After filtration, washing, and drying, the composite powder was obtained. The mass ratio of deionized water, zinc oxide, cerium oxide, polyethylene glycol 400, and hexamethylenetetramine is 260:10-12:7-8:1.0-1.2:1.8-2.2. 3. Silane-modified aluminum hydroxide Aluminum hydroxide was dried at 110-113℃ for 4.0-4.2h to obtain dried aluminum hydroxide. The modified liquid was sprayed onto the surface of the dried aluminum hydroxide while the stirring speed was controlled at 380-410rpm. After spraying, stirring was continued for 20-30min. The temperature was raised to 50-53℃ and stirring was continued for 3-4h. After filtration, washing and drying, silane-modified aluminum hydroxide was obtained. The mass ratio of the modified liquid to aluminum hydroxide is 81-82:10-18; The modified liquid is prepared by mixing γ-aminopropyltriethoxysilane with anhydrous ethanol and stirring until homogeneous. In the modified solution, the mass ratio of γ-aminopropyltriethoxysilane to 80g anhydrous ethanol is 1.0-2.0:80.

[0012] 4. Mixing Modified aluminum hypophosphite, silane-modified aluminum hydroxide, zinc borate, 2,3-dimethyl-2,3-diphenylbutane, and composite powder are heated to 65-70℃ and stirred at 440-460 rpm for 10-13 min. Then, melamine polyphosphate (MPP), antioxidant 1010, and zinc stearate are added, and stirring is continued for 7-8 min. Finally, anti-dripping agent PTFE and lubricant EBS are added, and stirring is carried out at 150-170 rpm for 3-4 min to obtain a low-halogen compound flame retardant. The mass ratio of the modified aluminum hypophosphite, silane-modified aluminum hydroxide, zinc borate, 2,3-dimethyl-2,3-diphenylbutane, composite powder, melamine polyphosphate (MPP), antioxidant 1010, zinc stearate, anti-dripping agent PTFE, and lubricant EBS is 15-20:10-15:5-8:5-8:5-8:3-5:0.3-0.5:0.5-1.0:0.3-0.5:0.2-0.3.

[0013] A low-halogen compound flame retardant for dripping non-flammable cotton is prepared using the aforementioned method.

[0014] This invention modifies and coats aluminum hypophosphite by forming an organic coating layer on the surface of aluminum hypophosphite using a melamine / formaldehyde / amino-terminated polyether compound modifier. Formaldehyde undergoes pre-condensation polymerization with melamine and amino-terminated polyether, while the amino groups of the amino-terminated polyether form hydrogen bonds with the hydroxyl groups on the surface of aluminum hypophosphite, achieving adsorption of the modifier on the aluminum hypophosphite surface. Melamine derivatives form a dense organic film on the surface of aluminum hypophosphite, improving dispersibility in the polymer carrier, enhancing thermal stability, and constructing a nitrogen-phosphorus synergistic flame retardant system. This system, in synergy with subsequent composite powders and silane-modified aluminum hydroxide, significantly improves the char-forming properties, smoke suppression, and anti-dripping performance of the composite material, meeting the low-halogen, high-efficiency flame retardant requirements of dripping non-flammable cotton. In the preparation of composite powder, a dispersion is first prepared using cerium oxide and zinc oxide, and the cerium oxide is then subjected to Ce... 3+ / Ce 4+ The redox cycle captures combustion free radicals, rapidly forming a stable char layer. Zinc oxide effectively inhibits flue gas release and synergistically strengthens the char layer structure. Polyethylene glycol can resist particle aggregation, and hexamethylenetetramine can improve system stability. Under the action of sodium hydroxide solution, zinc oxide dissolves to produce Zn(OH)₄. 2- Cerium oxide undergoes surface hydroxylation under alkaline hydrothermal conditions. Under these conditions, hexamethylenetetramine accelerates hydrolysis, releasing ammonia and formaldehyde. Ammonia further maintains the alkalinity of the system, while formaldehyde assists in particle bonding. Zn(OH)₄ 2- It migrates to the surface of cerium oxide and adsorbs and deposits on the hydroxyl sites to form a stable zinc oxide-cerium oxide composite powder. It is uniformly dispersed and has strong high-temperature stability. In synergy with modified aluminum hypophosphite, silane-modified aluminum hydroxide, nitrogen-based flame retardants, etc., it achieves organic-inorganic compounding, which can significantly improve smoke suppression performance and achieve low-halogen and high-efficiency flame retardant effect.

[0015] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The low-halogen compound flame retardant prepared by this invention is used in composite materials obtained from PP. The addition amount of the low-halogen compound flame retardant is 7.0 wt%, the flame retardant rating is V-0, the limiting oxygen index is 35.33-37.82%, and the cantilever beam impact strength is 7.12-7.28 kJ / m. 2 The tensile strength is 33.45-35.56 MPa, the elongation at break is 48.50-50.32 MPa, and the flexural strength is 42.65-45.47 MPa. 2. The low-halogen compound flame retardant prepared by this invention is used in composite materials obtained from PE. The addition amount of the low-halogen compound flame retardant is 4.0 wt%, the flame retardant rating is V-0, the limiting oxygen index is 37.51-39.43%, and the cantilever beam impact strength is 9.33-9.64 kJ / m. 2 The tensile strength is 36.56-38.42 MPa, the elongation at break is 52.78-53.64 MPa, and the flexural strength is 44.84-46.88 MPa. The low-halogen compound flame retardant prepared in this invention was used in composite materials obtained from PE. The composites were aged in an 80℃ oven for 8 days, allowed to naturally return to room temperature, and then aged again in a 120℃ oven for 8 days, allowed to naturally return to room temperature. The cantilever beam impact strength was then measured to be 8.80-9.24 kJ / m². 2 The tensile strength is 34.62-36.96 MPa, and the flexural strength is 42.69-45.52 MPa. Detailed Implementation

[0016] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0017] Example 1 1. Modified coating of aluminum hypophosphite Add 500 mL of anhydrous ethanol to a three-necked flask and stir at 400 r / min. Heat to 45 °C, add 1000 g of aluminum hypophosphite, and stir continuously for 35 min. Add 80 g of compound modifier in three portions, with an interval of 5 min between each addition. After the addition is complete, keep warm and stir for 60 min. Increase the speed to 600 r / min and raise the temperature to 65 °C at a rate of 2.5 °C / min. Stir and reflux for 3 h. After filtration, dry at -0.09 MPa and 90 °C for 10 h to obtain modified aluminum hypophosphite. The preparation method of the compound modifier is as follows: 50g of melamine and 50g of 37wt% formaldehyde solution are mixed, 1.5g of amino-terminated polyether is added while stirring, and after stirring evenly, 8wt% sodium hydroxide solution is added to adjust the pH to 97 to obtain the compound modifier. The terminal amino polyether has a molecular weight of 230, a total amine value of 8.7 meq / g, a primary amine content of 98%, and a viscosity of 9.8 cSt at 25°C.

[0018] 2. Preparation of composite powder Add 12g of zinc oxide and 8g of cerium oxide to 260g of deionized water, stir well, then add 1.2g of polyethylene glycol 400 and 2.2g of hexamethylenetetramine. Disperse ultrasonically for 35min at a power of 320W and a frequency of 40kHz. After ultrasonic dispersion, raise the temperature to 63℃, add 5wt% sodium hydroxide solution at a rate of 2mL / min, and control the pH value to 10.5. Transfer to a hydrothermal reactor, raise the temperature to 155℃ at a rate of 2.5℃ / min, and maintain the temperature for 4h. After the reaction, allow to cool naturally to room temperature, filter, wash, and dry to obtain the composite powder.

[0019] 3. Silane-modified aluminum hydroxide Aluminum hydroxide was dried at 113℃ for 4.0h to obtain dried aluminum hydroxide. 82g of the modified liquid was sprayed onto the surface of 18g of dried aluminum hydroxide. The stirring speed was controlled at 410rpm during spraying. After spraying, stirring was continued for 30min. The temperature was raised to 53℃ and stirring was continued for 4h. After filtration, washing and drying, silane-modified aluminum hydroxide was obtained. The modified liquid is prepared by mixing 2.0g of γ-aminopropyltriethoxysilane with 80g of anhydrous ethanol and stirring until homogeneous.

[0020] 4. Mixing 20g of modified aluminum hypophosphite, 15g of silane-modified aluminum hydroxide, 8g of zinc borate, 8g of 2,3-dimethyl-2,3-diphenylbutane, and 8g of composite powder were mixed and heated to 70℃ and stirred at 460rpm for 13min. Then, 5g of melamine polyphosphate (MPP), 0.5g of antioxidant 1010, and 1.0g of zinc stearate were added, and stirring was continued for 8min. Finally, 0.5g of anti-dripping agent PTFE and 0.3g of lubricant EBS were added, and stirring was carried out at 170rpm for 3min to obtain a low-halogen compound flame retardant.

[0021] Example 2 1. Modified coating of aluminum hypophosphite Add 500 mL of anhydrous ethanol to a three-necked flask and stir at 300 r / min. Heat to 40 °C, add 1000 g of aluminum hypophosphite, and stir continuously for 30 min. Add 50 g of compound modifier in three portions, with an interval of 5 min between each addition. After the addition is complete, keep warm and stir for 55 min. Increase the speed to 500 r / min and raise the temperature to 60 °C at a rate of 2.0 °C / min. Stir and reflux for 2 h. After filtration, dry at -0.08 MPa and 80 °C for 8 h to obtain modified aluminum hypophosphite. The preparation method of the compound modifier is as follows: 30g of melamine and 40g of 35wt% formaldehyde solution are mixed, 0.5g of amino-terminated polyether is added while stirring, and after stirring evenly, 5wt% sodium hydroxide solution is added to adjust the pH to 7 to obtain the compound modifier. The terminal amino polyether has a molecular weight of 230, a total amine value of 8.1 meq / g, a primary amine content of 97%, and a viscosity of 9.2 cSt at 25°C.

[0022] 2. Preparation of composite powder Add 10g of zinc oxide and 7g of cerium oxide to 260g of deionized water, stir well, then add 1.0g of polyethylene glycol 400 and 1.8g of hexamethylenetetramine. Disperse ultrasonically for 30min at a power of 300W and a frequency of 38kHz. After ultrasonic dispersion, raise the temperature to 60℃, add 4wt% sodium hydroxide solution at a rate of 3mL / min, and control the pH value to 10.0. Transfer to a hydrothermal reactor, raise the temperature to 145℃ at a rate of 2.0℃ / min, and maintain the temperature for 3h. After the reaction, allow it to cool naturally to room temperature, filter, wash, and dry to obtain the composite powder.

[0023] 3. Silane-modified aluminum hydroxide Aluminum hydroxide was dried at 110℃ for 4.2h to obtain dried aluminum hydroxide. 81g of the modified liquid was sprayed onto the surface of 10g of dried aluminum hydroxide. The stirring speed was controlled at 380rpm during spraying. After spraying, stirring was continued for 20min. The temperature was raised to 50℃ and stirring was continued for 3h. After filtration, washing and drying, silane-modified aluminum hydroxide was obtained. The modified liquid is prepared by mixing 1.0g of γ-aminopropyltriethoxysilane with 80g of anhydrous ethanol and stirring until homogeneous.

[0024] 4. Mixing 15g of modified aluminum hypophosphite, 10g of silane-modified aluminum hydroxide, 5g of zinc borate, 5g of 2,3-dimethyl-2,3-diphenylbutane, and 5g of composite powder were mixed and heated to 65℃ and stirred at 440 rpm for 10 min. Then, 3g of melamine polyphosphate (MPP), 0.3g of antioxidant 1010, and 0.5g of zinc stearate were added, and stirring was continued for 7 min. Finally, 0.3g of anti-dripping agent PTFE and 0.2g of lubricant EBS were added, and stirring was carried out at 150 rpm for 4 min to obtain a low-halogen compound flame retardant.

[0025] Example 3 1. Modified coating of aluminum hypophosphite 500 mL of anhydrous ethanol was first added to a three-necked flask and stirred at 350 r / min. The mixture was heated to 43 °C, and 1000 g of aluminum hypophosphite was added. The mixture was stirred continuously for 32 min. 60 g of compound modifier was added in four portions, with an interval of 4 min between each addition. After the addition was completed, the mixture was kept warm and stirred for 57 min. The stirring speed was increased to 550 r / min, and the temperature was increased to 62 °C at a rate of 2.3 °C / min. The mixture was stirred and refluxed for 3 h. After filtration, the mixture was dried at 85 °C under a vacuum of -0.09 MPa for 9 h to obtain modified aluminum hypophosphite. The preparation method of the compound modifier is as follows: 40g of melamine and 45g of 36wt% formaldehyde solution are mixed, 1.0g of amino-terminated polyether is added while stirring, and after stirring evenly, 6wt% sodium hydroxide solution is added to adjust the pH to 8 to obtain the compound modifier. The terminal amino polyether has a molecular weight of 230, a total amine value of 8.4 meq / g, a primary amine content of 98%, and a viscosity of 9.5 cSt at 25°C.

[0026] 2. Preparation of composite powder Add 12g of zinc oxide and 8g of cerium oxide to 260g of deionized water, stir well, then add 1.2g of polyethylene glycol 400 and 2.0g of hexamethylenetetramine. Sonicate for 33min at a power of 310W and a frequency of 40kHz. After ultrasonic dispersion, raise the temperature to 62℃, add 5wt% sodium hydroxide solution at a rate of 2mL / min, and control the pH value to 10.3. Transfer to a hydrothermal reactor, raise the temperature to 150℃ at a rate of 2.3℃ / min, and maintain the temperature for 3.5h. After the reaction, allow to cool naturally to room temperature, filter, wash, and dry to obtain the composite powder.

[0027] 3. Silane-modified aluminum hydroxide Aluminum hydroxide was dried at 112℃ for 4.2 h to obtain dried aluminum hydroxide. 82 g of the modified liquid was sprayed onto the surface of 14 g of dried aluminum hydroxide while the stirring speed was controlled at 400 rpm. After the spraying was completed, the stirring was continued for 25 min, the temperature was raised to 52℃, and the stirring was continued for 3.5 h. After filtration, washing and drying, silane-modified aluminum hydroxide was obtained. The modified liquid is prepared by mixing 1.5g of γ-aminopropyltriethoxysilane with 80g of anhydrous ethanol and stirring until homogeneous.

[0028] 4. Mixing 18g of modified aluminum hypophosphite, 13g of silane-modified aluminum hydroxide, 7g of zinc borate, 7g of 2,3-dimethyl-2,3-diphenylbutane, and 6g of composite powder were mixed and heated to 67℃ and stirred at 450 rpm for 12 min. Then, 4g of melamine polyphosphate (MPP), 0.4g of antioxidant 1010, and 0.7g of zinc stearate were added, and stirring was continued for 7.5 min. Finally, 0.4g of anti-dripping agent PTFE and 0.3g of lubricant EBS were added, and stirring was carried out at 160 rpm for 4 min to obtain a low-halogen compound flame retardant.

[0029] Comparative Example 3.1 Based on Example 3, the following changes were made: The steps for preparing the composite powder are as follows: 12g of zinc oxide and 8g of cerium oxide are added to 260g of deionized water and stirred evenly. Then, 1.2g of polyethylene glycol 400 and 2.0g of hexamethylenetetramine are added and ultrasonically dispersed for 33min. The ultrasonic power is 310W and the ultrasonic frequency is 40kHz. After ultrasonic dispersion, the powder is filtered, washed and dried to obtain the composite powder. Omit the silane-modified aluminum hydroxide step; replace the silane-modified aluminum hydroxide in the mixing step with an equal amount of untreated aluminum hydroxide; The rest of the operations are exactly the same.

[0030] Comparative Example 3.2 Based on Example 3, the following changes were made: The modification and coating step of aluminum hypophosphite is omitted; the modified aluminum hypophosphite in the mixing step is replaced with an equal amount of untreated aluminum hypophosphite. The rest of the operations are exactly the same.

[0031] Performance testing 1. Application of low-halogen compound flame retardants in PP Low-halogen compound flame retardants prepared in Examples 1-3, Comparative Examples 3.1, and Comparative Example 3.2 were added to a PP (Sinopec 1100N) carrier, with an addition amount of 7.0 wt%. After being mixed evenly, the mixture was fed into a twin-screw extruder for extrusion. The die head temperature of the twin-screw extruder was controlled at 200°C, and the temperatures of zones 1 to 8 were 150°C, 180°C, 180°C, 200°C, 200°C, 200°C, 180°C, and 180°C, respectively. The screw speed was 250 rpm. After cooling, the mixture was pelletized and dried, and then fed into an injection molding machine for injection molding. The injection molding machine pressure was controlled at 75 bar, the mold temperature was 40°C, and the temperatures of zones 1 to 5 were 180°C, 200°C, 200°C, 200°C, and 170°C, respectively. Composite material test specimens were obtained. The performance of the obtained composite material test specimens was tested, and the test results are as follows:

[0032] 2. Application of low-halogen compound flame retardants in PE Low-halogen compound flame retardants prepared in Examples 1-3, Comparative Examples 3.1, and Comparative Examples 3.2 were added to a PE (Sinopec 1100N) carrier, with an addition amount of 4 wt%. After being mixed evenly, the mixture was fed into a twin-screw extruder for extrusion. The die head temperature of the twin-screw extruder was controlled at 140°C, and the temperatures of zones one through eight were 120°C, 135°C, 145°C, 150°C, 150°C, 145°C, 140°C, and 135°C, respectively. The screw speed was 200 rpm. After cooling, the mixture was pelletized and dried, and then fed into an injection molding machine for injection molding. The injection molding machine pressure was controlled at 75 bar, the mold temperature was 30°C, and the temperatures of zones one through five were 175°C, 180°C, 180°C, 180°C, and 165°C, respectively. Composite material test specimens were obtained. The performance of the obtained composite material test specimens was tested, and the test results are as follows:

[0033] The composite material test specimens obtained in Examples 1-3, Comparative Example 3.1, and Comparative Example 3.2 were aged in an 80℃ oven for 8 days, allowed to naturally return to room temperature, and then aged in a 120℃ oven for 8 days, allowed to naturally return to room temperature. The cantilever beam impact strength, tensile strength, and flexural strength were then tested again. The test results are as follows:

[0034] According to the results in the table above, the composite powder of Comparative Example 3.1 is a mixture of cerium oxide and zinc oxide. It has not undergone hydrothermal reaction and is only in a simple physical mixture state. Furthermore, the aluminum hydroxide has not been modified with silane, has strong surface hydrophilicity, poor compatibility with hydrophobic polymers, and is prone to agglomeration, forming stress concentration points. This results in low mechanical strength and poor thermal stability in PP and PE applications. Unmodified aluminum hydroxide will absorb moisture and undergo thermo-oxidative aging at high temperatures, and the composite powder will agglomerate locally, resulting in a low strength retention rate after the thermal aging test. Comparative Example 3.1 retains modified aluminum hypophosphite, and its flame retardant effect is higher than that of Comparative Example 3.2, but it cannot reach the level of Example 3. Comparative Example 3.2, which was not modified with aluminum hypophosphite, retained the composite powder and silane-modified aluminum hydroxide components. It had better dispersion performance and mechanical properties than Comparative Example 3.1. However, the untreated aluminum hypophosphite agglomerated and had poor compatibility with PP and PE. When heated, the flame retardant could not decompose uniformly and could not form a continuous and dense char layer, resulting in a decrease in flame retardancy. It would also form cracks during aging and had a low strength retention rate after heat aging.

[0035] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0036] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a low-halogen compound flame retardant for dripping non-flammable cotton, characterized in that, The process includes the modification and coating of aluminum hypophosphite, the preparation of composite powder, the silane-modified aluminum hydroxide, and the mixing steps. The modification and coating steps of the aluminum hypophosphite are as follows: aluminum hypophosphite is added to anhydrous ethanol, stirred evenly, the compound modifier is added in 3-4 portions, the mixture is kept warm and stirred for 55-60 minutes, and then stirred and refluxed at 60-65℃ for 2-3 hours to obtain modified aluminum hypophosphite. The preparation method of the compound modifier is as follows: melamine and formaldehyde solution are mixed, amino-terminated polyether is added, and after stirring evenly, sodium hydroxide solution is added to adjust the pH to 7-9 to obtain the compound modifier. The steps for preparing the composite powder are as follows: zinc oxide and cerium oxide are added to deionized water and stirred evenly. Then, polyethylene glycol 400 and hexamethylenetetramine are added, and the mixture is ultrasonically dispersed for 30-35 minutes. The temperature is then raised to 60-63°C, and sodium hydroxide solution is added to control the pH value to 10.0-10.

5. The mixture is then transferred to a hydrothermal reactor, heated to 145-155°C, and kept at this temperature for 3-4 hours to obtain the composite powder.

2. The method for preparing a low-halogen compound flame retardant for dripping non-combustible cotton according to claim 1, characterized in that, In the modified coating step of aluminum hypophosphite, the volume-to-mass ratio of anhydrous ethanol, aluminum hypophosphite, and compound modifier is 500mL:1000g:50-80g. In the preparation method of the compound modifier, the terminal amino polyether has a molecular weight of 230, a total amine value of 8.1-8.7 meq / g, a primary amine rate of 97-98%, and a viscosity of 9.2-9.8 cSt at 25°C. The mass ratio of melamine, formaldehyde solution, and amino-terminated polyether is 30-50:40-50:0.5-1.

5.

3. The method for preparing a low-halogen compound flame retardant for dripping non-flammable cotton according to claim 1, characterized in that, In the step of preparing the composite powder, the mass ratio of deionized water, zinc oxide, cerium oxide, polyethylene glycol 400, and hexamethylenetetramine is 260:10-12:7-8:1.0-1.2:1.8-2.

2.

4. The method for preparing a low-halogen compound flame retardant for dripping non-flammable cotton according to claim 1, characterized in that, The steps for silane-modified aluminum hydroxide are as follows: aluminum hydroxide is dried at 110-113℃ for 4.0-4.2h to obtain dried aluminum hydroxide; the modification liquid is sprayed onto the surface of the dried aluminum hydroxide while the stirring speed is controlled at 380-410rpm; after spraying, stirring is continued for 20-30min; the temperature is raised to 50-53℃ and stirring is continued for 3-4h; after filtration, washing and drying, silane-modified aluminum hydroxide is obtained.

5. The method for preparing a low-halogen compound flame retardant for dripping non-flammable cotton according to claim 4, characterized in that, The mass ratio of the modified liquid to aluminum hydroxide is 81-82:10-18.

6. The method for preparing a low-halogen compound flame retardant for dripping non-combustible cotton according to claim 4, characterized in that, The modified liquid is prepared by mixing γ-aminopropyltriethoxysilane with anhydrous ethanol and stirring until homogeneous. In the modified solution, the mass ratio of γ-aminopropyltriethoxysilane to 80g anhydrous ethanol is 1.0-2.0:

80.

7. The method for preparing a low-halogen compound flame retardant for dripping non-combustible cotton according to claim 1, characterized in that, The mixing step involves heating modified aluminum hypophosphite, silane-modified aluminum hydroxide, zinc borate, 2,3-dimethyl-2,3-diphenylbutane, and composite powder to 65-70°C and stirring at 440-460 rpm for 10-13 minutes. Then, melamine polyphosphate (MPP), antioxidant 1010, and zinc stearate are added, and stirring continues for 7-8 minutes. Finally, anti-dripping agent PTFE and lubricant EBS are added, and stirring is performed at 150-170 rpm for 3-4 minutes to obtain a low-halogen compound flame retardant.

8. The method for preparing a low-halogen compound flame retardant for dripping non-flammable cotton according to claim 7, characterized in that, The mass ratio of the modified aluminum hypophosphite, silane-modified aluminum hydroxide, zinc borate, 2,3-dimethyl-2,3-diphenylbutane, composite powder, melamine polyphosphate (MPP), antioxidant 1010, zinc stearate, anti-dripping agent PTFE, and lubricant EBS is 15-20:10-15:5-8:5-8:5-8:3-5:0.3-0.5:0.5-1.0:0.3-0.5:0.2-0.

3.

9. A low-halogen compound flame retardant for dripping non-flammable cotton, characterized in that, Prepared by the preparation method according to any one of claims 1-8.

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