High-strength flame-retardant plastic and preparation method thereof

Abstract

The present application provides a high-strength flame-retardant plastic and a preparation method thereof. The high-strength flame-retardant plastic is composed of the following components: pre-irradiated cage-type silsesquioxane reinforced polypropylene, a flame retardant compound, a flame retardant synergist, a lubricant, and an antioxidant. The flame retardant compound includes at least two compounds of a hyperbranched triazine carbonizing agent, ammonium polyphosphate, melamine polyphosphate, and antimony trioxide. The prepared high-strength flame-retardant plastic has stable carbonization and mechanical properties. By using pre-irradiated cage-type silsesquioxane to reinforce polypropylene, free radicals are generated on the surface of the cage-type silsesquioxane, which can form chemical bonds with the polypropylene chain and enhance the interfacial bonding force, thereby offsetting the loss of mechanical properties caused by the addition of flame retardants. On the other hand, it can also offset the problem of poor thermal stability of polypropylene after irradiation.

Description

Technical Field

[0001] The present application relates to the technical field of polymer materials, and in particular to a high-strength flame-retardant plastic and a preparation method thereof. Background Art

[0002] In recent years, polypropylene (PP) has been widely used in a variety of fields, including construction, home furnishings, and industry, due to its advantages such as light weight, corrosion resistance, and easy processing. However, PP has a low oxygen index and produces significant dripping during combustion, which makes it unable to meet the requirements for use in live fire protection applications and requires flame retardant modification. Polypropylene has extremely poor charring properties and a melting point far below its degradation temperature. Large addition amounts are required to achieve satisfactory anti-drip properties, which reduces its strength. Intumescent flame retardants (IFRs) have low smoke generation, low toxicity, and are more environmentally friendly, and are gradually replacing bromine-antimony flame retardants as the mainstream application in the industry. However, traditional IFRs have low flame retardant efficiency and require large addition amounts, making it difficult to guarantee the mechanical properties of polypropylene. Summary of the Invention

[0003] In view of this, in order to solve at least one of the above technical problems, an embodiment of the present application provides a high-strength flame-retardant plastic.

[0004] The present invention provides a high-strength flame-retardant plastic comprising, by weight, 70-94 parts of pre-irradiated caged silsesquioxane-reinforced polypropylene, 10-25 parts of a flame retardant compound, 0.5-5 parts of a flame retardant synergist, 0.5-2.1 parts of a lubricant, and 0.4-0.8 parts of an antioxidant. The flame retardant compound comprises a combination of at least two of a hyperbranched triazine carbonizing agent, ammonium polyphosphate, melamine polyphosphate, and antimony trioxide.

[0005] In one embodiment of the present application, the flame retardant composite is prepared by compounding a hyperbranched triazine carbonizing agent, melamine polyphosphate and antimony trioxide in a weight ratio of 2:1:1.

[0006] In another embodiment of the present application, the flame retardant composite is prepared by compounding a hyperbranched triazine carbonizing agent, ammonium polyphosphate and antimony trioxide in a weight ratio of 3:2:1.

[0007] In some embodiments of the present application, the preparation method of the pre-irradiated cage-type silsesquioxane-enhanced polypropylene comprises the following steps: drying the polypropylene and cage-type silsesquioxane in a vacuum oven at 60°C to 80°C for 10 to 12 hours to remove surface moisture, adding molybdenum salt powder and introducing liquid nitrogen to stir and mix at a stirring rate of 1000 rpm to 1500 rpm to obtain a premix. The premix is ​​melt-granulated to obtain a first mixture. The first mixture is dried in a vacuum oven at 60°C to 80°C for 8 to 10 hours, and then heated to 400 rpm. 60The first mixture is subjected to γ-irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane-reinforced polypropylene.

[0008] In some embodiments of the present application, the irradiation treatment parameters are: irradiation dose rate of 30 kGy / h to 80 kGy / h, irradiation dose of 40 kGy to 80 kGy, and irradiation time of 0.5 h to 2 h.

[0009] In some embodiments of the present application, the weight ratio of the polypropylene to the cage-type silsesquioxane is 100:(0.8-3), and the weight ratio of the polypropylene to the molybdenum salt is 100:(12-35).

[0010] In some embodiments of the present application, the molybdenum salt is any one of sodium molybdate, ammonium octamolybdate, and potassium molybdate.

[0011] In some embodiments of the present application, the flame retardant synergist is nano zirconium phosphate.

[0012] In some embodiments of the present application, the polypropylene has a melt index of 1.8 g / min to 3.5 g / min, an isotacticity of 98.5%, and a relative molecular mass distribution M w / M n ≥6, ash content ≤0.03%.

[0013] In addition, an embodiment of the present application also provides a method for preparing the aforementioned high-strength flame-retardant plastic, comprising the following steps: pre-irradiated cage-type silsesquioxane-reinforced polypropylene, flame retardant compound, flame retardant synergist, lubricant, and antioxidant are placed into a reactor and blended by weight, with a shear rate of 100 rpm to 200 rpm and a temperature of 180°C to 220°C for 10 to 15 minutes, and granulated to obtain a high-strength flame-retardant plastic.

[0014] Compared with the prior art, the high-strength flame-retardant plastic provided in the embodiment of the present application has stable charring and mechanical properties. By using pre-irradiated cage-type silsesquioxane to enhance polypropylene, free radicals are generated on the surface of the cage-type silsesquioxane, which can form chemical bonds with the polypropylene chain and enhance the interfacial bonding force, thereby offsetting the loss of mechanical properties caused by the addition of flame retardants. On the other hand, the problem of poor thermal stability of polypropylene after irradiation is offset. At the same time, the cross-linked network of cage-type silsesquioxane and polypropylene produced by irradiation treatment can form a high thermal stability graphitized carbon layer structure during the combustion process, thereby protecting the internal matrix and delaying its degradation process. It further increases the melt strength and provides higher shear stress in the subsequent blending stage, forcing the flame retardant composite particles to break and disperse evenly. The hyperbranched triazine carbonizing agent adsorbs other flame retardant components through the entanglement of molecular chains, further inhibiting agglomeration and ensuring a balance between flame retardant efficiency and mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the SEM image of the premix in Comparative Example 2 of this application.

[0016] Figure 2 This is the SEM image of the premix in Example 1 of the present application. DETAILED DESCRIPTION

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present application in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0018] When polypropylene burns, high temperatures trigger melt flow, which can cause molten material to drip, exacerbating the spread of fire and increasing the risk of combustion. Suppressing droplet formation has become a key technical challenge in expanding the application of polypropylene in areas with high fire safety requirements. Currently, droplet suppression is mainly achieved by introducing flame retardants to promote the formation of a dense char layer on the burning surface, thereby isolating heat and oxygen transfer. Intumescent flame retardant systems (IFRs) exhibit significant advantages in the field of polypropylene flame retardancy due to their low smoke and low toxicity during combustion. However, traditional IFR systems generally suffer from poor thermal stability and low flame retardant efficiency. To achieve the ideal flame retardant effect, high proportions of additives are often required, resulting in a significant deterioration in the material's mechanical strength and processing properties. Therefore, the development of efficient IFR systems requires ensuring flame retardant properties while maximizing the mechanical properties and thermal stability of the base material. As a core component of IFR, the carbonization efficiency and density of the residual char structure of the charring agent directly determine the thermal insulation properties of the intumescent char layer, which in turn affects the overall flame retardant performance.

[0019] To this end, the present invention provides a high-strength flame-retardant plastic, comprising, by weight, 70-94 parts of pre-irradiated caged silsesquioxane-reinforced polypropylene, 10-25 parts of a flame retardant compound, 0.5-5 parts of a flame retardant synergist, 0.5-2.1 parts of a lubricant, and 0.4-0.8 parts of an antioxidant. The flame retardant compound comprises a combination of at least two of a hyperbranched triazine carbonizing agent, ammonium polyphosphate, melamine polyphosphate, and antimony trioxide.

[0020] Compared to the prior art, the high-strength flame-retardant plastic provided in the embodiment of the present application has stable charring and mechanical properties. By using pre-irradiated cage-type silsesquioxane to enhance polypropylene, free radicals are generated on the surface of the cage-type silsesquioxane, which can form chemical bonds with polypropylene chains and enhance interfacial bonding, thereby offsetting the loss of mechanical properties caused by the addition of flame retardants. On the other hand, the problem of poor thermal stability of polypropylene after irradiation is offset. At the same time, the cross-linked network of cage-type silsesquioxane and polypropylene produced by irradiation can form a high thermal stability graphitized carbon layer structure during combustion, thereby protecting the internal matrix and delaying its degradation process. It further increases the melt strength and provides higher shear stress in the subsequent blending stage, forcing the flame retardant composite particles to break and disperse evenly. The hyperbranched triazine carbonizing agent adsorbs other flame retardant components through molecular chain entanglement. Its highly branched three-dimensional structure quickly cross-links to form a dense carbon layer during combustion, and the pre-irradiated POSS enhances the rigidity of the carbon layer skeleton through chemical cross-linking, making the carbon layer less prone to cracking at high temperatures. Further suppressing agglomeration ensures a balance between flame retardant efficiency and mechanical properties.

[0021] In some embodiments of the present application, the flame retardant composite is a hyperbranched triazine carbonizing agent, melamine polyphosphate and antimony trioxide compounded in a weight ratio of 2:1:1. The hyperbranched triazine carbonizing agent promotes the formation of a carbon layer at high temperature, effectively isolating heat and oxygen, and the melamine polyphosphate (phosphorus / nitrogen flame retardant) promotes the dehydration of the substrate into carbon by decomposing phosphoric acid, while releasing non-combustible gas to dilute the oxygen concentration. The efficient carbonization of hyperbranched triazine complements the gas source effect of MPP, forming an expanded carbon layer during combustion. At the same time, when antimony trioxide is compounded with phosphorus / nitrogen-containing flame retardants, the gas phase combustion chain reaction is suppressed by generating free radical scavengers such as SbPO4. On the other hand, in combination with irradiated polypropylene, melt dripping can be reduced and the vertical combustion level can be significantly improved.

[0022] In another embodiment of the present application, the flame retardant composite is formed by compounding a hyperbranched triazine charring agent, ammonium polyphosphate, and antimony trioxide in a weight ratio of 3:2:1. The flame retardant properties of polypropylene are enhanced by compounding ammonium polyphosphate, a hyperbranched triazine charring agent, and antimony trioxide. The benzene rings and triazine groups in the triazine charring agent participate in the formation of a char layer and improve its quality. When antimony trioxide is compounded with a phosphorus / nitrogen-containing flame retardant, it generates free radical scavengers such as SbPO4, thereby suppressing the gas-phase combustion chain reaction.

[0023] In some embodiments of the present application, the flame retardant synergist is nano-zirconium phosphate. The catalytic carbonization effect of nano-zirconium phosphate improves the quality of the polypropylene carbon layer, thereby enhancing the carbon layer's ability to suppress heat and gas flow during combustion, further enhancing the flame retardancy of polypropylene. When compounded with ammonium polyphosphate, a charring agent, and other agents, ZrP enhances flame retardancy through a dual mechanism of catalysis and barrier properties, while also improving the mechanical properties and processing fluidity of polypropylene.

[0024] In some embodiments of the present application, the lubricant is either paraffin wax or polyethylene wax, and the antioxidant is either antioxidant 1010 or antioxidant 2246.

[0025] In some embodiments of the present application, the method for preparing the pre-irradiated cage silsesquioxane reinforced polypropylene comprises the following steps:

[0026] Step S01: Dry polypropylene and cage-type silsesquioxane in a vacuum oven at 60°C to 80°C for 10 to 12 hours to remove surface moisture. This can effectively remove moisture and low-molecular volatiles adsorbed on the surface of the material, reduce the risk of hydrolysis or phase separation caused by residual moisture in subsequent processing, and improve the thermal stability and interfacial bonding strength of the material. Add molybdenum salt powder and introduce liquid nitrogen to stir and mix at a stirring rate of 1000 rpm to 1500 rpm to obtain a premix. By introducing liquid nitrogen into the reaction system to achieve low-temperature mixing, the cage-type silsesquioxane particles can be refined through the embrittlement effect and reduce agglomeration caused by polarity differences. This premixing process can also avoid the thermal degradation of the cage-type silsesquioxane that may be caused by direct mixing at high temperature, ensure the integrity of its cage structure, and thus give full play to the role of enhancing interfacial bonding during the subsequent irradiation cross-linking process. In some embodiments, the particle size of polypropylene is 10 μm to 80 μm. The particle size of cage-type silsesquioxane is 1.5 nm to 3 nm. The particle size of the molybdenum salt is 200 nm to 250 nm. Optionally, the cage silsesquioxane is octaepoxy cage silsesquioxane.

[0027] In some embodiments, the drying temperature may be 60° C., 70° C., and 80° C. The drying time may be 10 h, 11 h, and 12 h. The stirring speed may be 1000 rpm, 1200 rpm, 1300 rpm, and 1500 rpm.

[0028] In some embodiments of the present application, the weight ratio of the polypropylene to the cage-type silsesquioxane is 100:(10-20), and the weight ratio of the polypropylene to the molybdenum salt is 100:(12-35).

[0029] In some embodiments, the weight ratio of the polypropylene to the cage-type silsesquioxane can be 100:10, 100:12, 100:15, and 100:20. If the weight ratio of the polypropylene to the cage-type silsesquioxane is less than 100:10, the reinforcing effect is not significant. The weight ratio of the polypropylene to the molybdenum salt can be 100:12, 100:20, 100:32, and 100:35.

[0030] In some embodiments of the present application, the molybdenum salt is any one of sodium molybdate, ammonium octamolybdate, and potassium molybdate. In some embodiments, the molybdenum salt is ammonium octamolybdate. By adding a molybdenum salt to the polypropylene irradiation system, the formation of the irradiation cross-linked structure of the polypropylene is promoted.

[0031] In some embodiments of the present application, the polypropylene has a melt index of 1.8 g / min to 3.5 g / min, an isotacticity of 98.5%, and a relative molecular mass distribution M w / M n ≥6, ash content ≤0.03%.

[0032] Step S02: melt and granulate the premix to obtain a first mixture.

[0033] Step S03: Dry the first mixture in a vacuum oven at 60°C to 80°C for 8 hours to 10 hours. 60 The first mixture is subjected to γ-irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane-reinforced polypropylene.

[0034] In some embodiments of the present application, the irradiation treatment parameters are: irradiation dose rate of 30 kGy / h to 80 kGy / h, irradiation dose of 40 kGy to 80 kGy, and irradiation time of 1 h to 2 h.

[0035] In some embodiments, the irradiation dose rate may be 30 kGy / h, 40 kGy / h, 60 kGy / h, and 80 kGy / h, the irradiation dose may be 40 kGy, 60 kGy, and 80 kGy, and the irradiation time may be 0.5 h, 1 h, and 2 h.

[0036] In addition, the present invention also provides a method for preparing the aforementioned high-strength flame-retardant plastic, which specifically includes the following steps:

[0037] Step S1: Place pre-irradiated caged silsesquioxane reinforced polypropylene, flame retardant compound, flame retardant synergist, lubricant and antioxidant into a reactor for melt blending according to weight, with a shear rate of 100 to 200 rpm and a temperature of 180° C. to 220° C. for 10 to 15 minutes.

[0038] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0039] Step S2: Extruding and granulating the blend to obtain a high-strength flame-retardant plastic.

[0040] In some embodiments, the shear rate may be 100 rpm, 150 rpm, and 200 rpm, the shear temperature may be 180° C., 190° C., and 200° C., and the mixing time may be 10 min, 12 min, 13 min, and 15 min.

[0041] Compared with the prior art, the preparation method of the high-strength flame-retardant plastic provided in the embodiment of the present application has the following advantages:

[0042] Beneficial effects:

[0043] This preparation method is simple and efficient, is conducive to the large-scale production of high-strength flame-retardant plastics, and has excellent commercial prospects.

[0044] The above-mentioned high-strength flame-retardant plastic and its preparation method are further described below through specific examples.

[0045] Example 1

[0046] Step 1: Polypropylene and octa-epoxy cage silsesquioxane were dried in a vacuum oven at 80°C for 12 hours to remove surface moisture in a weight ratio of 100:10. Ammonium octamolybdate was added in a weight ratio of 100:20 and liquid nitrogen was introduced and stirred at a stirring rate of 1000 rpm to obtain a premix. The premix was melt-granulated to obtain a first mixture. The first mixture was dried in a vacuum oven at 80°C for 8 hours and then used. 60 The first mixture is subjected to gamma irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane-reinforced polypropylene, wherein the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0047] Step 2: Melt and blend 78 parts by weight of pre-irradiated caged silsesquioxane-reinforced polypropylene, 15 parts of a flame retardant compound, 1 part of nano-zirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 parts of antioxidant 1010 in a reactor at a shear rate of 100 rpm and a temperature of 180°C for 15 minutes. The mixture is extruded and pelletized to produce a high-strength flame-retardant plastic. The flame retardant compound is a mixture of a hyperbranched triazine carbonizing agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0048] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0049] Example 2

[0050] Step 1: Polypropylene and octa-epoxy cage silsesquioxane were dried in a vacuum oven at 80°C for 12 hours to remove surface moisture in a weight ratio of 100:10. Ammonium octamolybdate was added in a weight ratio of 100:20 and liquid nitrogen was introduced and stirred at a stirring rate of 1000 rpm to obtain a premix. The premix was melt-granulated to obtain a first mixture. The first mixture was dried in a vacuum oven at 80°C for 8 hours and then used. 60 The first mixture is subjected to gamma irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane-reinforced polypropylene, wherein the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0051] Step 2: Melt and blend 78 parts by weight of pre-irradiated caged silsesquioxane-reinforced polypropylene, 15 parts of a flame retardant compound, 1 part of nano-zirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 parts of antioxidant 1010 in a reactor at a shear rate of 100 rpm and a temperature of 180°C for 15 minutes. The mixture is extruded and pelletized to produce a high-strength flame-retardant plastic. The flame retardant compound is a mixture of a hyperbranched triazine carbonizing agent, ammonium polyphosphate, and antimony trioxide in a weight ratio of 3:2:1.

[0052] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0053] Example 3

[0054] Step 1: Polypropylene and octa-epoxy cage silsesquioxane were dried in a vacuum oven at 80°C for 12 hours to remove surface moisture. Ammonium octamolybdate was added in a weight ratio of 100:20 and liquid nitrogen was introduced and stirred at a stirring rate of 1000 rpm to obtain a premix. The premix was melt-granulated to obtain a first mixture. The first mixture was dried in a vacuum oven at 80°C for 8 hours and then used. 60 The first mixture is subjected to gamma irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane-reinforced polypropylene, wherein the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0055] Step 2: Melt and blend 78 parts by weight of pre-irradiated caged silsesquioxane-reinforced polypropylene, 15 parts of a flame retardant compound, 1 part of nano-zirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 parts of antioxidant 1010 in a reactor at a shear rate of 100 rpm and a temperature of 180°C for 15 minutes. The mixture is extruded and pelletized to produce a high-strength flame-retardant plastic. The flame retardant compound is a mixture of a hyperbranched triazine carbonizing agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0056] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0057] Example 4

[0058] Step 1: Polypropylene and octa-epoxy cage-type silsesquioxane were dried in a vacuum oven at 80°C for 12 hours to remove surface moisture in a weight ratio of 100:15. Ammonium octamolybdate was added in a weight ratio of 100:20 and liquid nitrogen was introduced and stirred at a stirring rate of 1000 rpm to obtain a premix. The premix was melt-granulated to obtain a first mixture. The first mixture was dried in a vacuum oven at 80°C for 8 hours and used 60 The first mixture is subjected to gamma irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane-reinforced polypropylene, wherein the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0059] Step 2: Melt and blend 78 parts by weight of pre-irradiated caged silsesquioxane-reinforced polypropylene, 15 parts of a flame retardant compound, 1 part of nano-zirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 parts of antioxidant 1010 in a reactor at a shear rate of 100 rpm and a temperature of 180°C for 15 minutes. The mixture is extruded and pelletized to produce a high-strength flame-retardant plastic. The flame retardant compound is a mixture of a hyperbranched triazine carbonizing agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0060] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0061] Example 5

[0062] Step 1: Polypropylene and octa-epoxy cage silsesquioxane were dried in a vacuum oven at 80°C for 12 hours to remove surface moisture in a weight ratio of 100:20. Ammonium octamolybdate was added in a weight ratio of 100:32 and liquid nitrogen was introduced and stirred at a stirring rate of 1000 rpm to obtain a premix. The premix was melt-granulated to obtain a first mixture. The first mixture was dried in a vacuum oven at 80°C for 8 hours and then used. 60 The first mixture is subjected to gamma irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane-reinforced polypropylene, wherein the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0063] Step 2: Melt and blend 78 parts by weight of pre-irradiated caged silsesquioxane-reinforced polypropylene, 15 parts of a flame retardant compound, 1 part of nano-zirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 parts of antioxidant 1010 in a reactor at a shear rate of 100 rpm and a temperature of 180°C for 15 minutes. The mixture is extruded and pelletized to produce a high-strength flame-retardant plastic. The flame retardant compound is a mixture of a hyperbranched triazine carbonizing agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0064] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0065] Example 6

[0066] Step 1: Polypropylene and octa-epoxy cage silsesquioxane were dried in a vacuum oven at 80°C for 12 hours to remove surface moisture in a weight ratio of 100:10. Ammonium octamolybdate was added in a weight ratio of 100:35 and liquid nitrogen was introduced and stirred at a stirring rate of 1000 rpm to obtain a premix. The premix was melt-granulated to obtain a first mixture. The first mixture was dried in a vacuum oven at 80°C for 8 hours and then used. 60 The first mixture is subjected to gamma irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane-reinforced polypropylene, wherein the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0067] Step 2: Melt and blend 78 parts by weight of pre-irradiated caged silsesquioxane-reinforced polypropylene, 15 parts of a flame retardant compound, 1 part of nano-zirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 parts of antioxidant 1010 in a reactor at a shear rate of 100 rpm and a temperature of 180°C for 15 minutes. The mixture is extruded and pelletized to produce a high-strength flame-retardant plastic. The flame retardant compound is a mixture of a hyperbranched triazine carbonizing agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0068] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0069] Example 7

[0070] Step 1: Polypropylene and octaepoxy cage silsesquioxane were dried in a vacuum oven at 80°C for 12 hours to remove surface moisture. Ammonium octamolybdate was added in a weight ratio of 100:12 and liquid nitrogen was introduced and stirred at a stirring rate of 1000 rpm to obtain a premix. The premix was melt-granulated to obtain a first mixture. The first mixture was dried in a vacuum oven at 80°C for 8 hours and then used. 60 The first mixture is subjected to gamma irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane-reinforced polypropylene, wherein the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0071] Step 2: Melt and blend 78 parts by weight of pre-irradiated caged silsesquioxane-reinforced polypropylene, 15 parts of a flame retardant compound, 1 part of nano-zirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 parts of antioxidant 1010 in a reactor at a shear rate of 100 rpm and a temperature of 180°C for 15 minutes. The mixture is extruded and pelletized to produce a high-strength flame-retardant plastic. The flame retardant compound is a mixture of a hyperbranched triazine carbonizing agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0072] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0073] Comparative Example 1

[0074] 78 parts by weight of polypropylene, 15 parts of a flame retardant compound, 1 part of nano-zirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 parts of antioxidant 1010 were melt-blended in a reactor at a shear rate of 100 rpm and a temperature of 180°C for 15 minutes. The mixture was extruded and pelletized to obtain the product. The flame retardant compound is a mixture of a hyperbranched triazine carbonizing agent, ammonium polyphosphate, and antimony trioxide in a weight ratio of 3:2:1.

[0075] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0076] Comparative Example 2

[0077] Step 1: Polypropylene and octa-epoxy cage silsesquioxane were dried in a vacuum oven at 80°C for 12 hours to remove surface moisture in a weight ratio of 100:10. Ammonium octamolybdate was added in a weight ratio of 100:20 and stirred at a stirring rate of 1000 rpm to obtain a premix. The premix was melt-granulated to obtain a first mixture. The first mixture was dried in a vacuum oven at 80°C for 8 hours and then used. 60 The first mixture is subjected to gamma irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane-reinforced polypropylene, wherein the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0078] Step 2: Melt and blend 78 parts by weight of pre-irradiated caged silsesquioxane-reinforced polypropylene, 15 parts of a flame retardant compound, 1 part of nano-zirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 parts of antioxidant 1010 in a reactor at a shear rate of 100 rpm and a temperature of 180°C for 15 minutes. The mixture is extruded and pelletized to produce a high-strength flame-retardant plastic. The flame retardant compound is a mixture of a hyperbranched triazine carbonizing agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0079] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0080] Comparative Example 3

[0081] Step 1: Polypropylene and octa-epoxy cage silsesquioxane were dried in a vacuum oven at 80°C for 12 hours to remove surface moisture and then introduced into liquid nitrogen for stirring at a stirring rate of 1000 rpm to obtain a premix. The premix was melt-granulated to obtain a first mixture. The first mixture was dried in a vacuum oven at 80°C for 8 hours and then used 60 The first mixture is subjected to gamma irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane-reinforced polypropylene, wherein the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0082] Step 2: Melt and blend 78 parts by weight of pre-irradiated caged silsesquioxane-reinforced polypropylene, 15 parts of a flame retardant compound, 1 part of nano-zirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 parts of antioxidant 1010 in a reactor at a shear rate of 100 rpm and a temperature of 180°C for 15 minutes. The mixture is extruded and pelletized to produce a high-strength flame-retardant plastic. The flame retardant compound is a mixture of a hyperbranched triazine carbonizing agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0083] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0084] Comparative Example 4

[0085] Step 1: Polypropylene and octa-epoxy cage silsesquioxane were dried in a vacuum oven at 80°C for 12 hours to remove surface moisture in a weight ratio of 100:10. Ammonium octamolybdate was added in a weight ratio of 100:20 and liquid nitrogen was introduced and stirred at a stirring rate of 1000 rpm to obtain a premix. The premix was melt-granulated to obtain a first mixture. The first mixture was dried in a vacuum oven at 80°C for 8 hours and then used. 60 The first mixture is subjected to gamma irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane-reinforced polypropylene, wherein the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0086] Step 2: Melt and blend 78 parts by weight of pre-irradiated caged silsesquioxane-reinforced polypropylene, 15 parts of a hyperbranched triazine carbonizer, 1 part of nano-zirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 parts of antioxidant 1010 in a reactor at a shear rate of 100 rpm and a temperature of 180°C for 15 minutes. The blend was extruded and pelletized to obtain a high-strength flame-retardant plastic.

[0087] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0088] Comparative Example 5

[0089] Step 1: Polypropylene and octaepoxy cage silsesquioxane were dried in a vacuum oven at 80°C for 12 hours to remove surface moisture in a 100:10 weight ratio. Ammonium octamolybdate was added in a 100:20 weight ratio and liquid nitrogen was introduced with stirring at 1000 rpm to obtain a premix. The premix was melt-granulated to obtain a first mixture.

[0090] Step 2: Melt and blend 78 parts by weight of the first mixture from Step 1, 15 parts of the flame retardant compound, 1 part of nano-zirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 parts of antioxidant 1010 in a reaction kettle at a shear rate of 100 rpm and a temperature of 180°C for 15 minutes. The mixture is extruded and pelletized to produce a high-strength flame-retardant plastic. The flame retardant compound is composed of a hyperbranched triazine carbonizing agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0091] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0092] Comparative Example 6

[0093] Step 1: Dry polypropylene in a vacuum oven at 80°C for 12 hours to remove surface moisture. Add polypropylene and ammonium octamolybdate in a weight ratio of 100:20 to a reaction vessel and introduce liquid nitrogen and stir to mix at a stirring rate of 1000 rpm to obtain a premix. Melt the premix and granulate to obtain a first mixture. Dry the first mixture in a vacuum oven at 80°C for 8 hours and use 60 The first mixture is subjected to gamma irradiation treatment using a Co source to obtain the pre-irradiated polypropylene, wherein the irradiation dose is 40 kGy and the irradiation dose rate is 80 kGy / h.

[0094] Step 2: Melt and blend 78 parts by weight of pre-irradiated caged silsesquioxane-reinforced polypropylene, 15 parts of a flame retardant compound, 1 part of nano-zirconium phosphate, 1.5 parts of polyethylene wax, and 0.3 parts of antioxidant 1010 in a reactor at a shear rate of 100 rpm and a temperature of 180°C for 15 minutes. The mixture is extruded and pelletized to produce a high-strength flame-retardant plastic. The flame retardant compound is a mixture of a hyperbranched triazine carbonizing agent, melamine polyphosphate, and antimony trioxide in a weight ratio of 2:1:1.

[0095] Among them, the head temperature is 190℃, the temperature of zone 1 is 200℃, the temperature of zone 2 is 210℃, the temperature of zone 3 is 220℃, the temperature of zone 4 is 210℃, and the temperature of zone 5 is 200℃.

[0096] The premixes obtained in Example 1 and Comparative Example 2 were characterized using scanning electron microscopy. Figure 1 and 2 As shown, the premixture in Example 1 was evenly dispersed after the liquid nitrogen was introduced, while the premixture in Comparative Example 2 agglomerated.

[0097] The high-strength flame-retardant plastics in Examples 1-7 and Comparative Examples 1-6 were subjected to the following performance tests:

[0098] 1. The board meets the UL-94 / 3.2mm test requirements and has a fire rating of V0.

[0099] 2. The limiting oxygen index of flame retardant polypropylene is determined according to the combustion behavior standard of GB / T 2406.2-2009 using the oxygen index method.

[0100] 3. Impact strength and tensile strength test.

[0101]

[0102]

[0103] The above results show that:

[0104] The flame retardant in Example 1 is melamine polyphosphate (MPP), which has better synergy between acid source and gas source than ammonium polyphosphate (APP) in Example 2, so the LOI is higher. In Example 2, due to the lower decomposition temperature of APP, the thermal stability may be slightly reduced, resulting in slightly lower impact strength.

[0105] As can be seen from Example 1 and Comparative Example 1, the flame-retardant plastic made from commercially available polypropylene without the addition of pre-irradiated cage silsesquioxane-reinforced polypropylene lacks nano-reinforcement and interfacial crosslinking, significantly reducing matrix strength. While it passes the flame retardancy test and reaches V-2, its impact and tensile strengths are significantly reduced.

[0106] Combine Figure 1 and Figure 2 As can be seen from Example 1 and Comparative Example 2, liquid nitrogen is not passed into the reaction, and reunion occurs easily. Due to the difference in surface energy, and particle diameter is different, easy friction occurs bonding during the mixing and shearing process, thus reunite, causing the mechanical strength formed to be poor. On the other hand, poor dispersion causes flame retardant and POSS synergistic efficiency to reduce, and charcoal layer porosity increases.

[0107] As can be seen from Example 1 and Comparative Example 3, without the addition of ammonium octamolybdate, the crosslinking degree between polypropylene and cage silsesquioxane cannot be increased, and a crosslinking structure cannot be fully formed, resulting in a decrease in mechanical strength and flame retardancy.

[0108] As can be seen from Example 1 and Comparative Example 4, the use of a hyperbranched triazine char-forming agent alone, without the flame-retardant composite, lacks the synergistic effects of the acid source (MPP) and the gas source (antimony trioxide), resulting in an incomplete expanded char layer. A single flame retardant cannot form a multilayered carbon-gas barrier structure, weakening the flame retardant effect.

[0109] As can be seen from Example 1 and Comparative Example 5, without irradiation, direct pre-mixing, and only physical mixing of POSS and PP results in weak interfacial bonding and prone to interfacial debonding. No chemical cross-linking network is formed, resulting in decreased crack propagation resistance.

[0110] As can be seen from Example 1 and Comparative Example 6, without the addition of cage-type silsesquioxane, only irradiating polypropylene and molybdenum salts, the lack of the silicon-oxygen skeleton of POSS to strengthen the carbon layer, the flame retardant efficiency is low. Without POSS to synergize carbonization, the carbon layer easily collapses during combustion and cannot suppress molten droplets.

[0111] It can be seen from this that the high-strength flame-retardant plastic provided in the embodiment of the present application has stable charring and mechanical properties. By using pre-irradiated cage-type silsesquioxane to enhance polypropylene, free radicals are generated on the surface of cage-type silsesquioxane, which can form chemical bonds with polypropylene chains and enhance interfacial bonding, thereby offsetting the loss of mechanical properties caused by the addition of flame retardants. On the other hand, the problem of poor thermal stability of polypropylene after irradiation is offset. At the same time, the cross-linked network of cage-type silsesquioxane and polypropylene produced by irradiation can form a high thermal stability graphitized carbon layer structure during combustion, thereby protecting the internal matrix and delaying its degradation process. Further, the melt strength is increased, and higher shear stress is provided in the subsequent blending stage, forcing the flame retardant composite particles to break and evenly disperse. The hyperbranched triazine carbonizing agent adsorbs other flame retardant components through the entanglement of molecular chains. Its highly branched three-dimensional structure is rapidly cross-linked to form a dense carbon layer when burning, and the pre-irradiated POSS enhances the rigidity of the carbon layer skeleton by chemical cross-linking, making the carbon layer less prone to cracking at high temperatures. Further suppressing agglomeration ensures a balance between flame retardant efficiency and mechanical properties.

[0112] It will be understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications and improvements can be made without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A high-strength flame-retardant plastic, characterized in that: The invention is composed of the following components in parts by weight: 70-94 parts of pre-irradiated caged silsesquioxane-reinforced polypropylene, 10-25 parts of a flame retardant compound, 0.5-5 parts of a flame retardant synergist, 0.5-2.1 parts of a lubricant, and 0.4-0.8 parts of an antioxidant; wherein the flame retardant compound comprises a combination of at least two of a hyperbranched triazine carbonizing agent, ammonium polyphosphate, melamine polyphosphate, and antimony trioxide; The preparation method of the pre-irradiated cage-type silsesquioxane-enhanced polypropylene comprises the following steps: drying polypropylene and cage-type silsesquioxane in a vacuum oven at 60° C. to 80° C. for 10 to 12 hours to remove surface moisture, adding molybdenum salt powder and introducing liquid nitrogen with stirring and mixing at a stirring rate of 1000 rpm to 1500 rpm to obtain a premix; melt-granulating the premix to obtain a first mixture; drying the first mixture in a vacuum oven at 60° C. to 80° C. for 8 to 10 hours, and using 60 The first mixture is subjected to γ-irradiation treatment using a Co source to obtain the pre-irradiated cage-type silsesquioxane-reinforced polypropylene.

2. The high-strength flame-retardant plastic according to claim 1, characterized in that: The flame retardant composite is prepared by compounding a hyperbranched triazine carbonizing agent, melamine polyphosphate and antimony trioxide in a weight ratio of 2:1:

1.

3. The high-strength flame-retardant plastic according to claim 1, characterized in that: The flame retardant composite is prepared by compounding a hyperbranched triazine carbonizing agent, ammonium polyphosphate and antimony trioxide in a weight ratio of 3:2:

1.

4. The high-strength flame-retardant plastic according to claim 1, characterized in that: The irradiation treatment parameters are: irradiation dose rate of 30 kGy / h to 80 kGy / h, irradiation dose of 40 kGy to 80 kGy, and irradiation time of 0.5 h to 2 h.

5. The high-strength flame-retardant plastic according to claim 1, characterized in that: The weight ratio of the polypropylene to the cage-type silsesquioxane is 100:(10-20), and the weight ratio of the polypropylene to the molybdenum salt is 100:(12-35).

6. The high-strength flame-retardant plastic according to claim 1, characterized in that: The molybdenum salt is any one of sodium molybdate, ammonium octamolybdate and potassium molybdate.

7. The high-strength flame-retardant plastic according to claim 6, characterized in that: The flame retardant synergist is nano zirconium phosphate.

8. The high-strength flame-retardant plastic according to claim 1, characterized in that: The polypropylene has a melt index of 1.8 g / min to 3.5 g / min, an isotacticity of 98.5%, and a relative molecular mass distribution M w / M n ≥6, ash content ≤0.03%.

9. A method for preparing a high-strength flame-retardant plastic according to any one of claims 1 to 8, characterized in that: The following steps are involved: Pre-irradiated cage silsesquioxane reinforced polypropylene, flame retardant compound, flame retardant synergist, lubricant and antioxidant are placed into a reactor and blended by weight. The mixture is mixed at a shear rate of 100 rpm to 200 rpm and a temperature of 180°C to 220°C for 10 min to 15 min, and granulated to obtain a high-strength flame retardant plastic.

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