Polypropylene composite flame retardant and preparation method of polypropylene composite

Abstract

A flame retardant for polypropylene composite materials is characterized by being prepared through the following steps: ammonium polyphosphate, 2-hydroxy-3-methylpyridine, and a solvent are added to a stirring vessel and stirred until homogeneous. The temperature is then raised, long-chain fatty acids are added, and the reaction continues with stirring. The mixture is cooled to room temperature, filtered, washed with deionized water, and dried to constant weight to obtain the polypropylene composite flame retardant. This invention also discloses a method for preparing polypropylene composite materials. The polypropylene composite material of this invention exhibits excellent flame retardancy and can be widely used in the preparation of machinery, automotive, electronic, construction, textile, and packaging products.

Description

Technical Field

[0001] This invention relates to a flame retardant formulation, and more particularly to a flame retardant for use in polypropylene composite materials. This invention also relates to the preparation of polypropylene, belonging to the field of polymer materials technology. Background Technology

[0002] Polypropylene (PP) is a high-performance thermoplastic synthetic resin with advantages such as non-toxicity, corrosion resistance, electrical insulation, and excellent processing properties, making it widely used in construction, machinery, electronics, textiles, and packaging. However, PP is extremely flammable, with a limiting oxygen index (LoI) of only 18, and it generates a large amount of heat and smoke during combustion, posing a significant threat to life and property safety. Therefore, it is necessary to develop effective strategies for flame-retardant treatment of PP materials.

[0003] Polypropylene itself lacks reactive groups, making intrinsic flame retardancy difficult to achieve through chemical modification. Therefore, flame retardant modification of polypropylene is usually achieved by adding external flame retardants. Flame retardants used for polypropylene include halogenated flame retardants, inorganic flame retardants, and intumescent flame retardants. Halogenated flame retardants have excellent flame retardant effects, but pose a risk of releasing corrosive gases and carcinogenic substances during combustion, endangering human health. Inorganic flame retardants have low flame retardant efficiency, requiring high addition amounts to achieve the desired effect, severely impacting the material's mechanical properties. Intumescent flame retardants are low in smoke and toxicity, environmentally friendly and highly efficient, making them a relatively ideal flame retardant for PP. However, existing intumescent flame retardants still suffer from high usage costs and significant impact on mechanical properties.

[0004] Therefore, many improved flame retardants have been disclosed in the prior art for application in polypropylene. See Chinese invention patent application number ZL201210066018.2, "A Halogen-Free Environmentally Friendly Flame Retardant for Polypropylene" (authorization announcement number CN102585375B); and also see Chinese invention patent application publication number 202311820190.7, "A Halogen-Free Flame Retardant Polypropylene Material and Its Preparation Method" (application publication number CN 117700885A). Summary of the Invention

[0005] The first technical problem to be solved by the present invention is to provide a flame retardant for polypropylene composite materials with good flame retardancy, in view of the above-mentioned technical status.

[0006] The second technical problem to be solved by the present invention is to provide a method for preparing a polypropylene composite material with good flame retardancy, in view of the above-mentioned technical status.

[0007] The technical solution adopted by the present invention to solve the first technical problem mentioned above is: a flame retardant for polypropylene composite materials, characterized by being prepared through the following steps:

[0008] Ammonium polyphosphate, 2-hydroxy-3-methylpyridine, and solvent were added to a stirring vessel and stirred until homogeneous. The temperature was then raised to 70–80°C, and long-chain fatty acids were added. The mixture was stirred and reacted for 4–5 hours. The mixture was cooled to room temperature, filtered, washed with deionized water, and dried to constant weight to obtain a polypropylene composite flame retardant. The weight ratio of the aforementioned ammonium polyphosphate, 2-hydroxy-3-methylpyridine, and long-chain fatty acids was 20–30:15–20:40–50.

[0009] Preferably, the solvent is at least one of dichloromethane, trichloromethane, and dimethyl sulfoxide.

[0010] Preferably, the long-chain fatty acid is at least one of stearic acid, palmitic acid, myristic acid, and lauric acid.

[0011] The technical solution adopted by the present invention to solve the second technical problem mentioned above is: a method for preparing a polypropylene composite material, characterized by comprising the following steps:

[0012] Polypropylene, a flame retardant for polypropylene composites, and a modified char agent are mixed evenly and then kneaded to obtain polypropylene composite granules.

[0013] Preferably, the weight ratio of the polypropylene, polypropylene composite flame retardant, and modified charring agent is 100-120:1-2:1-2.

[0014] Furthermore, the modified charring agent is prepared through the following steps:

[0015] Place halloysite nanotubes and deionized water into a reaction vessel, stir, add zinc nitrate hexahydrate, adjust the pH to between 5 and 6, react at 70-80℃ for 2-3 hours, filter after the reaction is complete, wash the filter cake with deionized water, and then dry the filter cake to obtain the intermediate product.

[0016] Add the intermediate product, molecular sieve and solvent to a container, heat to 80-90℃ and react for 3-4 hours. After the reaction is complete, filter, wash the filter cake with deionized water, and then dry the filter cake to obtain the modified char agent.

[0017] The aforementioned halloysite nanotubes and zinc nitrate hexahydrate have a weight ratio of 10–20:2–4; the aforementioned intermediate product and molecular sieve have a weight ratio of 3–5:8–10.

[0018] Preferably, the solvent is at least one of diethylene glycol dimethyl ether, propylene glycol, and ethylene glycol dimethyl ether.

[0019] Preferably, the mixing conditions are as follows: zone 1 temperature 170-180℃, zone 2 temperature 170-180℃, zone 3 temperature 170-180℃, screw speed 60-70 rpm, and processing time 10-20 min.

[0020] Compared with existing technologies, the advantages of this invention are as follows: First, by reacting ammonium polyphosphate with 2-hydroxy-3-methylpyridine, a phosphorus- and nitrogen-containing flame retardant is synthesized. The combined use of phosphorus and nitrogen elements can effectively exert quenching, dilution, and cooling effects in the gas phase, as well as a shielding effect in the condensed phase, resulting in the best overall flame retardant and smoke-suppressing performance. Second, by encapsulating this flame retardant with long-chain fatty acids, the surface polarity of the flame retardant is effectively reduced, and the interaction force between the flame retardant and the matrix is ​​enhanced. This effectively improves the dispersibility of the flame retardant in the matrix, allowing for more uniform char formation during combustion, and providing insulation against heat and combustible gases in the condensed phase.

[0021] The introduction of modified charring agents involves loading Zn ions onto inorganic nanoparticle charring agents via ion exchange, followed by grafting these onto molecular sieves. The synergistic effect of the inorganic nanoparticle charring agent and the organic flame retardant enhances the density and continuity of the char layer, significantly reducing heat and smoke release during composite combustion. Loading Zn ions onto the inorganic nanoparticle charring agent aims to leverage the excellent catalytic effect of Zn ions, which rapidly facilitates a synergistic effect between the inorganic nanoparticle charring agent and the organic flame retardant. Molecular sieves possess stable structural properties, making them an excellent carrier. Furthermore, they can adsorb small molecule gases released during combustion, reducing the release of toxic gases.

[0022] The polypropylene composite material of the present invention has good flame retardancy and can be widely used in the preparation of machinery, automobiles, electronic appliances, construction, textiles and packaging products. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the embodiments.

[0024] Example 1:

[0025] ① Add 20g of ammonium polyphosphate and 15g of 2-hydroxy-3-methylpyridine to a three-necked flask containing 200ml of dichloromethane. Stir the mixture for 20 minutes until homogeneous. Then raise the temperature to 70℃ and add 40g of stearic acid. Stir and react for 4 hours. Cool the mixture to room temperature, filter, wash three times with deionized water, and dry in an oven at 80℃ to constant weight to obtain a novel flame retardant.

[0026] ② Take 10g of halloysite nanotubes and add them to a three-necked flask containing 200ml of deionized water. Stir for 20min, add 2g of zinc nitrate hexahydrate, adjust the pH to 5 with 3mol / L acetic acid solution, and react at 70℃ for 2h. After the reaction is complete, filter and wash the filter cake three times with deionized water. Then dry the filter cake in an oven at 80℃ for 2h to obtain the intermediate product.

[0027] Take 3g of intermediate product and 8g of molecular sieve and add them to a three-necked flask containing 100ml of ethylene glycol dimethyl ether. Heat the flask to 80℃ and react for 3h. After the reaction is complete, filter the flask and wash the filter cake three times with deionized water. Then dry the filter cake in an oven at 80℃ for 2h to obtain the modified char agent.

[0028] ③ Mix 100g of polypropylene, 1g of novel flame retardant, and 1g of modified charcoal agent evenly and then knead. The kneading temperature is: 170℃ in zone 1, 170℃ in zone 2, and 170℃ in zone 3; the screw speed is 60 rpm, and the processing time is 10 min, to obtain polypropylene composite particles.

[0029] Example 2:

[0030] ① Add 25g of ammonium polyphosphate and 18g of 2-hydroxy-3-methylpyridine to a three-necked flask containing 250ml of dichloromethane. Stir the mixture for 25 minutes until homogeneous. Then raise the temperature to 75℃ and add 45g of stearic acid. Stir and react for 4.5 hours. Cool the mixture to room temperature, filter, wash three times with deionized water, and dry in an oven at 80℃ to constant weight to obtain a novel flame retardant.

[0031] ② Take 15g of halloysite nanotubes and add them to a three-necked flask containing 250ml of deionized water. Stir for 25min, add 3g of zinc nitrate hexahydrate, adjust the pH to 5.5 with 3mol / L acetic acid solution, and react at 75℃ for 2.5h. After the reaction is complete, filter and wash the filter cake three times with deionized water. Then dry the filter cake in an oven at 80℃ for 2h to obtain the intermediate product.

[0032] Take 4g of intermediate product and 9g of molecular sieve and add them to a three-necked flask containing 110ml of ethylene glycol dimethyl ether. Heat the flask to 85℃ and react for 3.5h. After the reaction is complete, filter the mixture and wash the filter cake three times with deionized water. Then dry the filter cake in an oven at 80℃ for 2h to obtain the modified char agent.

[0033] ③ Mix 110g of polypropylene, 1.5g of novel flame retardant, and 1.5g of modified charcoal agent evenly and then knead. The kneading temperature is: 175℃ in zone 1, 175℃ in zone 2, and 175℃ in zone 3; the screw speed is 65 rpm, and the processing time is 15 min, to obtain polypropylene composite particles.

[0034] Example 3:

[0035] ① Add 30g of ammonium polyphosphate and 20g of 2-hydroxy-3-methylpyridine to a three-necked flask containing 300ml of dichloromethane. Stir the mixture for 30 minutes until homogeneous. Then raise the temperature to 80℃ and add 50g of stearic acid. Stir and react for 5 hours. Cool the mixture to room temperature, filter, wash three times with deionized water, and dry in an oven at 80℃ to constant weight to obtain a novel flame retardant.

[0036] ② Take 20g of halloysite nanotubes and add them to a three-necked flask containing 300ml of deionized water. Stir for 30min, add 4g of zinc nitrate hexahydrate, adjust the pH to 6 with 3mol / L acetic acid solution, and react at 80℃ for 3h. After the reaction is complete, filter and wash the filter cake three times with deionized water. Then dry the filter cake in an oven at 80℃ for 2h to obtain the intermediate product.

[0037] Take 5g of intermediate product and 10g of molecular sieve and add them to a three-necked flask containing 120ml of ethylene glycol dimethyl ether. Heat the flask to 90℃ and react for 4h. After the reaction is complete, filter the flask and wash the filter cake three times with deionized water. Then dry the filter cake in an oven at 80℃ for 2h to obtain the modified char agent.

[0038] ③ Mix 120g of polypropylene, 2g of novel flame retardant, and 2g of modified charcoal agent evenly and then knead. The kneading temperature is: 180℃ in zone 1, 180℃ in zone 2, and 180℃ in zone 3; the screw speed is 70 rpm, and the processing time is 20 min, to obtain polypropylene composite particles.

[0039] Comparative Example 1:

[0040] ① Take 20g halloysite nanotubes and add them to a three-necked flask containing 300ml of deionized water. Stir for 30min, add 4g of zinc nitrate hexahydrate, adjust the pH to 6 with 3mol / L acetic acid solution, and react at 80℃ for 3h. After the reaction is complete, filter and wash the filter cake three times with deionized water. Then dry the filter cake in an oven at 80℃ for 2h to obtain the intermediate product.

[0041] Take 5g of intermediate product and 10g of molecular sieve and add them to a three-necked flask containing 120ml of ethylene glycol dimethyl ether. Heat the flask to 90℃ and react for 4h. After the reaction is complete, filter the flask and wash the filter cake three times with deionized water. Then dry the filter cake in an oven at 80℃ for 2h to obtain the modified char agent.

[0042] ② Mix 120g of polypropylene and 2g of modified carbonizing agent evenly and then knead. The kneading temperature is: 180℃ in zone 1, 180℃ in zone 2, and 180℃ in zone 3; the screw speed is 70 rpm and the processing time is 20 min to obtain polypropylene composite particles.

[0043] Comparative Example 1 does not introduce novel flame retardants

[0044] Comparative Example 2:

[0045] ① Add 30g of ammonium polyphosphate and 20g of 2-hydroxy-3-methylpyridine to a three-necked flask containing 300ml of dichloromethane. Stir the mixture for 30 minutes until homogeneous. Then raise the temperature to 80℃ and add 50g of stearic acid. Stir and react for 5 hours. Cool the mixture to room temperature, filter, wash three times with deionized water, and dry in an oven at 80℃ to constant weight to obtain a novel flame retardant.

[0046] ② Mix 120g of polypropylene and 2g of novel flame retardant evenly and then perform internal mixing. The processing temperature of the internal mixing is: 180℃ in zone 1, 180℃ in zone 2, and 180℃ in zone 3; the screw speed is 70 rpm, and the processing time is 20 min, to obtain polypropylene composite particles.

[0047] Comparative Example 2: No modified charring agent introduced

[0048] Comparative Example 3 did not introduce any new flame retardants or modified charring agents; it only used polypropylene for combustion performance testing.

[0049] Test methods: Polypropylene composite particles obtained in the above examples and comparative examples were prepared into samples using a flat vulcanizer at 180°C, and then cut into standard strips for vertical burning and oxygen index testing. Combustion performance: LOI standard testing was performed according to GB / T2406-2015, and UL-94 standard testing was performed according to GB / T 2408-2008.

[0050]

[0051] As can be seen from the table above, the polypropylene composite materials obtained in the various embodiments of the present invention have good flame retardant effects.

Claims

1. A flame retardant for polypropylene composite materials, characterized in that... Prepared by the following steps: Ammonium polyphosphate, 2-hydroxy-3-methylpyridine, and solvent were added to a stirring vessel and stirred until homogeneous. The temperature was then raised to 70–80°C, and long-chain fatty acids were added. The mixture was stirred and reacted for 4–5 hours. The mixture was cooled to room temperature, filtered, washed with deionized water, and dried to constant weight to obtain a polypropylene composite flame retardant. The weight ratio of the aforementioned ammonium polyphosphate, 2-hydroxy-3-methylpyridine, and long-chain fatty acids was 20–30:15–20:40–50.

2. The flame retardant for polypropylene composite materials according to claim 1, characterized in that... The solvent is at least one of dichloromethane, trichloromethane, and dimethyl sulfoxide.

3. The flame retardant for polypropylene composite materials according to claim 1, characterized in that... The long-chain fatty acid is at least one of stearic acid, palmitic acid, myristic acid, and lauric acid.

4. A method for preparing a polypropylene composite material using the polypropylene composite flame retardant according to any one of claims 1 to 3, characterized in that... Includes the following steps: Polypropylene, a flame retardant for polypropylene composites, and a char-modifying agent are mixed evenly and then kneaded to obtain polypropylene composite granules.

5. The preparation method according to claim 4, characterized in that... The weight ratio of the polypropylene, polypropylene composite flame retardant, and modified charring agent is 100-120:1-2:1-2.

6. The preparation method according to claim 4, characterized in that... The modified charring agent is prepared through the following steps: Place halloysite nanotubes and deionized water into a reaction vessel, stir, add zinc nitrate hexahydrate, adjust the pH to between 5 and 6, react at 70-80℃ for 2-3 hours, filter after the reaction is complete, wash the filter cake with deionized water, and then dry the filter cake to obtain the intermediate product. Add the intermediate product, molecular sieve and solvent to a container, heat to 80-90℃ and react for 3-4 hours. After the reaction is complete, filter, wash the filter cake with deionized water, and then dry the filter cake to obtain the modified char agent. The aforementioned halloysite nanotubes and zinc nitrate hexahydrate have a weight ratio of 10–20:2–4; the aforementioned intermediate product and molecular sieve have a weight ratio of 3–5:8–10.

7. The preparation method according to claim 6, characterized in that... The solvent is at least one of diethylene glycol dimethyl ether, propylene glycol, and ethylene glycol dimethyl ether.

8. The preparation method according to claim 4, characterized in that... The mixing conditions are as follows: Zone 1 temperature 170-180℃, Zone 2 temperature 170-180℃, Zone 3 temperature 170-180℃, screw speed 60-70 rpm, and processing time 10-20 min.

Images