Flame-retardant polypropylene composite material and preparation method thereof

Abstract

The present invention belongs to the technical field of polymer compound compositions and relates to flame-retardant polymer materials, specifically to a flame-retardant polypropylene composite material and a method for preparing the same. The present invention provides a flame-retardant polypropylene composite material comprising polypropylene, an intumescent flame retardant, a catalyst, a flame retardant additive, and a compatibilizer; the flame retardant additive is NOR 116 or GW-540; and the catalyst is a zinc-nickel bimetallic oxide catalyst. The present invention also provides a method for preparing the flame-retardant polypropylene composite material, comprising mixing the polypropylene, intumescent flame retardant, catalyst, flame retardant additive, and compatibilizer and then granulating the mixture. The method of the present invention can produce a polypropylene composite material with high flame retardancy.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer compound compositions, relates to flame-retardant polymer materials, and particularly relates to a flame-retardant polypropylene composite material and a preparation method thereof. Background Art

[0002] Polypropylene (PP) is a polymer formed by the polyaddition reaction of propylene. It is a colorless, odorless, non-toxic, translucent solid with excellent physical, chemical, and processing properties. Therefore, it is widely used in packaging materials, household items, medical devices, and automotive parts. However, the limiting oxygen index of pure PP is only 17% to 18%, making it flammable. Furthermore, PP produces large amounts of molten droplets when burned, which can easily ignite surrounding objects, posing a significant safety hazard.

[0003] As flame retardant technology evolves toward environmental friendliness, high efficiency, and smokelessness, halogenated flame retardants are gradually being replaced. Piperazine pyrophosphate (PAPP), a rising star, combines flame retardant elements such as P, N, and C, acting as a carbon source, gas source, and acid source. It also exhibits extremely high light and thermal stability, with a decomposition temperature exceeding 300°C at a 5% dosage, making it suitable for the processing temperatures of most resins. Preliminary research results indicate that compared to traditional intumescent flame retardants based on ammonium polyphosphate (APP), the PAPP system exhibits superior flame retardancy, requiring significantly lower dosage levels to achieve the same flame retardancy rating. Furthermore, it exhibits significant improvements in thermal stability and water precipitation resistance. However, due to the PAPP system's insufficient char-forming capacity, even at relatively low dosages, the PAPP intumescent flame retardant system still lacks a flame retardant rating in polypropylene.

[0004] Patent CN117430891A discloses flame retardant polypropylene by adding a phosphorus-nitrogen expansion system and introducing a magnesium-based synergist. However, the flame retardant effect is mediocre, and at least 24 parts of phosphorus-nitrogen flame retardant must be added to pass the V0 rating. Patent CN117700879A discloses a nickel-based bimetallic catalyst synergistically catalyzing an inorganic flame-retardant polypropylene carbonization flame-retardant composite material and its preparation method. The nickel-based catalyst is used as the main catalyst, and Al, Mg, and Co are used as the second metal. The activated carbon synergistically acidified by the nickel-based bimetallic catalyst is used to synergistically flame retard the inorganic flame-retardant polypropylene system carbonization flame-retardant composite material. Although the amount of inorganic flame retardant added is reduced compared to previous technologies, the total amount of flame retardant added exceeds 50% of the system, and the flame retardant efficiency is still very low.

[0005] NOR 116 is an N-alkoxy hindered amine flame retardant and light stabilizer produced by BASF. As a standalone flame retardant, it exhibits V2 flame retardancy in polyolefin fibers, nonwovens, and films. However, it has no flame retardant effect when used alone in thicker plastics. Patent CN116218077A discloses a halogen-free flame retardant masterbatch, a halogen-free flame retardant composite material, and its preparation and application. Using NOR 116 as a light stabilizer in combination with a metal hydroxide flame retardant and a phosphorus-based flame retardant, this system only achieves a V2 flame retardancy rating, resulting in low flame retardancy.

[0006] GW-540 is a hindered amine light stabilizer that inhibits or slows the degradation of polymer materials due to photooxidation. Patent CN116285407A discloses a high-flow tea residue / polypropylene composite material and its preparation method. It incorporates GW-540 as a light stabilizer, primarily to address aging and degradation issues during material processing. Currently, GW-540 is primarily used as a light stabilizer, with limited research on its use as a flame retardant additive. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a flame retardant polypropylene composite material with high flame retardancy and a preparation method thereof.

[0008] To solve the above technical problems, the present invention provides a flame-retardant polypropylene composite material (zinc-nickel bimetallic oxide catalytic synergistic flame-retardant polypropylene composite material), which is composed, by weight, of 80-85 parts of polypropylene, 14.5-18.7 parts of an intumescent flame retardant, 0.2-0.5 parts of a catalyst, 0.1-0.5 parts of a flame retardant additive, and 0.1-0.5 parts of a compatibilizer.

[0009] The flame retardant additive is NOR 116 or GW-540;

[0010] The catalyst is a zinc-nickel bimetallic oxide catalyst, and the zinc-nickel bimetallic oxide catalyst is Zn x Ni y O, x is any one from 0.7 to 0.9, y is any one from 0.1 to 0.3; and x+y=1.

[0011] As an improvement of the flame retardant polypropylene composite material of the present invention: x is 0.8, and y is 0.2.

[0012] As a further improvement of the flame-retardant polypropylene composite material of the present invention: the intumescent flame retardant is composed of a primary flame retardant and a secondary flame retardant, with the mass ratio of primary flame retardant to secondary flame retardant being 2 to 4:1; the primary flame retardant is piperazine pyrophosphate (PAPP), and the secondary flame retardant is any one of melamine polyphosphate (MPP), aluminum hypophosphite (HDP), and aluminum diethylphosphinate (ADP).

[0013] As a further improvement of the flame-retardant polypropylene composite material of the present invention: the compatibilizer is maleic anhydride grafted polypropylene or maleic anhydride grafted polyethylene.

[0014] As a further improvement of the flame-retardant polypropylene composite material of the present invention, the preparation method of the zinc-nickel bimetallic oxide catalyst is:

[0015] Dissolving zinc nitrate hexahydrate and nickel nitrate hexahydrate in distilled water under mechanical stirring to obtain a bimetallic solution; the mass ratio of zinc in the zinc nitrate hexahydrate to nickel in the nickel nitrate hexahydrate is 7-9:1-3;

[0016] Under stirring, the bimetallic solution is reacted at 80±10°C for 2±0.5 h. During the reaction, the pH of the reaction system is controlled at 8-9 (which can be controlled by adding 10% sodium carbonate solution).

[0017] After the reaction is completed, the mixture is aged (stationary aging) at 80±10°C for 1±0.2h, then filtered, and the filter cake is washed with deionized water (washed several times until the pH of the washing liquid is neutral), and then dried (force dried at 100~120°C for 4~6h), and then calcined at 450~550°C for 3.5~4.5h (calcination can be carried out in a muffle furnace), and then ground to obtain a zinc-nickel bimetallic oxide catalyst.

[0018] Note: Generally speaking, every 7-50g of nickel nitrate hexahydrate is dissolved in 200ml of distilled water.

[0019] The present invention also provides a method for preparing the flame-retardant polypropylene composite material, comprising the following steps:

[0020] (1) Weigh polypropylene, intumescent flame retardant, catalyst, flame retardant additive and compatibilizer in parts by weight and premix them in a mixer at 80±10℃ for 5±1 min; the premixing speed is 300±50 r / min;

[0021] (2) The mixed material obtained in step (1) is melted and sheared by a twin-screw extruder, and then extruded into granules. The extrusion temperature is 165-210 °C, the rotation speed is 450±50 r / min, and the feed speed is 30±3 r / min.

[0022] NOR 116 and GW-540 are primarily used in plastics to improve aging resistance. The present invention has discovered that these additives can capture free radicals generated by photooxidation and combustion degradation of polymers, thereby interrupting the chain reaction during combustion and providing a vapor-phase flame retardant effect. Therefore, in the specific formulations of the present invention, they can be used as flame retardant additives, resulting in unexpected flame retardant effects.

[0023] The present invention uses an intumescent flame retardant system based on PAPP, supplemented by MPP, HDP, and ADP. This system significantly improves flame retardancy compared to inorganic flame retardants and traditional APP systems. Given the PAPP system's insufficient charring capacity and the lack of flame retardancy in polypropylene at relatively low addition levels, the present invention uses a coprecipitation method to uniformly disperse ZnO and NiO to produce a zinc-nickel bimetallic oxide catalyst. At specific ratios, Zn and Ni synergistically catalyze the dehydrogenation of the PAPP system and polypropylene to form a high-quality carbon layer that isolates heat and prevents ignition of the polypropylene material. However, due to the rapid heat transfer of polypropylene, when the strip is ignited, the polypropylene rapidly degrades due to the heat, preventing the zinc-nickel bimetallic oxide catalyst from fully exerting its catalytic carbonization effect. Based on this, the present invention further adds NOR116 or GW-540 with gas phase flame retardant effect. When the spline is just ignited, NOR 116 or GW-540 can quickly degrade and capture active free radicals in the air, interrupting the chain decomposition reaction, exerting the gas phase flame retardant effect, and buying time for catalytic carbonization.

[0024] In the present invention, the role of the compatibilizer is to improve the compatibility and dispersibility of the intumescent flame retardant and the catalyst with the polypropylene, thereby enhancing the mechanical properties of the mixed material.

[0025] In summary, the present invention synergistically flame-retards polypropylene by complementing each other with the intumescent flame retardant, the zinc-nickel bimetallic oxide catalyst, and NOR 116 or GW-540 to obtain a polypropylene composite material with high flame retardancy. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0027] The raw materials used in the present invention are all commonly used raw materials in this field. For example:

[0028] Polypropylene was purchased from Baling Petrochemical, and piperazine pyrophosphate was produced by Shaoxing Xingxin New Materials Co., Ltd.; ammonium polyphosphate, melamine polyphosphate, aluminum hypophosphite, aluminum diethylphosphinate, and magnesium hydroxide were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; zinc nitrate hexahydrate, nickel nitrate hexahydrate, zinc oxide, and nickel oxide were purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; NOR 116 (BASF flame retardant NOR116, Germany) was purchased from Dafa Chemical Co., Ltd.; GW-540 (light stabilizer GW-540) and UV-770 (light stabilizer UV-770) were purchased from Shanghai Yihe Biotechnology Co., Ltd.; maleic anhydride-grafted polypropylene and maleic anhydride-grafted polyethylene were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0029] 1. Preparation of zinc-nickel bimetallic oxide catalyst:

[0030] Example 1: 51.17 g of zinc nitrate hexahydrate (containing 11.18 g of zinc) and 23.72 g of nickel nitrate hexahydrate (containing 4.79 g of nickel) were completely dissolved in 200 ml of distilled water under mechanical stirring to obtain a bimetallic solution.

[0031] The bimetallic solution was stirred at 80°C for 2 h. The pH of the reaction system was controlled at 8 during the reaction (this could be controlled by adding 10% sodium carbonate solution).

[0032] After the reaction, the mixture was aged at 80 °C for 1 h, then filtered, and the filter cake was washed with deionized water several times until the pH was neutral, then dried at 110 °C for 5 h, and finally calcined in a muffle furnace at 500 °C for 4 h. After grinding, it was passed through a 200-mesh sieve to obtain a zinc-nickel bimetallic oxide catalyst, which was recorded as Zn 0.7 Ni 0.3 O.

[0033] Example 2: 58.48 g of zinc nitrate hexahydrate (containing 12.76 g of zinc) and 15.80 g of nickel nitrate hexahydrate (containing 3.19 g of nickel) were completely dissolved in 200 ml of distilled water under mechanical stirring to obtain a bimetallic solution.

[0034] The bimetallic solution was reacted at 80°C for 2 h under stirring. The pH of the reaction system was controlled at 8.5 during the reaction (which could be controlled by adding 10% sodium carbonate solution).

[0035] After the reaction, the mixture was aged at 80 ° C for 1 h, then filtered, and the filter cake was washed with deionized water several times until the pH was neutral, then dried at 110 ° C for 5 h, and finally calcined in a muffle furnace at 500 ° C for 4 h. After grinding, it was passed through a 200-mesh sieve to obtain a zinc-nickel bimetallic oxide catalyst, which was recorded as Zn 0.8 Ni 0.2 O.

[0036] Example 3: 65.79 g of zinc nitrate hexahydrate (containing 14.37 g of zinc) and 7.92 g of nickel nitrate hexahydrate (containing 1.6 g of nickel) were completely dissolved in 200 ml of distilled water under mechanical stirring to obtain a bimetallic solution.

[0037] The bimetallic solution was reacted at 80°C for 2 h under stirring. The pH of the reaction system was controlled at 9 during the reaction (this could be controlled by adding a 10% sodium carbonate solution).

[0038] After the reaction, the mixture was aged at 80 ° C for 1 h, then filtered, and the filter cake was washed with deionized water several times until the pH was neutral, then dried at 110 ° C for 5 h, and finally calcined in a muffle furnace at 500 ° C for 4 h. After grinding, it was passed through a 200-mesh sieve to obtain a zinc-nickel bimetallic oxide catalyst, which was recorded as Zn 0.9 Ni 0.1 O.

[0039] Example 4: 29.24 g of zinc nitrate hexahydrate (containing 6.39 g of zinc) and 47.46 g of nickel nitrate hexahydrate (containing 9.58 g of nickel) were completely dissolved in 200 ml of distilled water under mechanical stirring to obtain a bimetallic solution;

[0040] The bimetallic solution was stirred at 80°C for 2 h. The pH of the reaction system was controlled at 8 during the reaction (this could be controlled by adding 10% sodium carbonate solution).

[0041] After the reaction, the mixture was aged at 80 ° C for 1 h, then filtered, and the filter cake was washed with deionized water several times until the pH was neutral, then dried at 110 ° C for 5 h, and finally calcined in a muffle furnace at 500 ° C for 4 h. After grinding, it was passed through a 200-mesh sieve to obtain a zinc-nickel bimetallic oxide catalyst, which was recorded as Zn 0.4 Ni 0.6 O.

[0042] Example 5: 36.55 g of zinc nitrate hexahydrate (containing 7.98 g of zinc) and 39.54 g of nickel nitrate hexahydrate (containing 7.98 g of nickel) were completely dissolved in 200 ml of distilled water under mechanical stirring to obtain a bimetallic solution.

[0043] The bimetallic solution was stirred at 80°C for 2 h. The pH of the reaction system was controlled at 8 during the reaction (this could be controlled by adding 10% sodium carbonate solution).

[0044] After the reaction, the mixture was aged at 80°C for 1 hour, and then filtered. The filter cake was washed with deionized water several times until the pH was neutral, and then dried at 110°C for 5 hours. Finally, it was calcined in a muffle furnace at 500°C for 4 hours. After grinding, it was passed through a 200-mesh sieve to obtain a zinc-nickel bimetallic oxide catalyst, which was recorded as Zn 0.5 Ni 0.5 O.

[0045] Example 6: 43.86 g of zinc nitrate hexahydrate (containing 9.58 g of zinc) and 31.64 g of nickel nitrate hexahydrate (containing 6.39 g of nickel) were completely dissolved in 200 ml of distilled water under mechanical stirring to obtain a bimetallic solution.

[0046] The bimetallic solution was stirred at 80°C for 2 h. The pH of the reaction system was controlled at 8 during the reaction (this could be controlled by adding 10% sodium carbonate solution).

[0047] After the reaction, the mixture was aged at 80 ° C for 1 h, then filtered, and the filter cake was washed with deionized water several times until the pH was neutral, then dried at 110 ° C for 5 h, and finally calcined in a muffle furnace at 500 ° C for 4 h. After grinding, it was passed through a 200-mesh sieve to obtain a zinc-nickel bimetallic oxide catalyst, which was recorded as Zn 0.6 Ni 0.4 O.

[0048] 2. Preparation of flame-retardant polypropylene composite materials (zinc-nickel bimetallic oxide catalytic synergistic flame-retardant polypropylene composite materials):

[0049] The following parts are by weight.

[0050] Example 1: A zinc-nickel bimetallic oxide catalyzed synergistic flame-retardant polypropylene composite material, having the following formula: 85 parts of polypropylene, 14.5 parts of an intumescent flame retardant, 0.2 parts of a zinc-nickel bimetallic oxide catalyst, 0.1 parts of a flame retardant additive, and 0.2 parts of a compatibilizer.

[0051] The intumescent flame retardant is composed of a primary flame retardant, piperazine pyrophosphate (PAPP), and a secondary flame retardant, melamine polyphosphate (MPP), with a mass ratio of PAPP / MPP=2:1.

[0052] The zinc-nickel bimetallic oxide catalyst is Zn 0.7 Ni 0.3 O;

[0053] The flame retardant additive is NOR 116;

[0054] The compatibilizer is maleic anhydride grafted polypropylene.

[0055] The preparation method is to carry out the following steps in sequence:

[0056] 1) Weigh polypropylene, intumescent flame retardant, zinc-nickel bimetallic oxide catalyst, flame retardant additive, and compatibilizer according to the formula, and premix them in a high-speed mixer at a high speed (speed of 300 r / min). The premixing temperature is 80°C and the premixing time is 5 minutes.

[0057] 2) The mixed material obtained in step 1) was melted and sheared in a twin-screw extruder, followed by extrusion granulation at an extrusion temperature of 165-210°C, a rotation speed of 450 r / min, and a feed speed of 30 r / min. The resulting particle size was approximately 2-3 mm.

[0058] Examples 2 to 11 were prepared in the same manner as in Example 1, except that the formulations were modified as shown in Table 1. In Table 1, the mass ratio of PAPP / MPP was 2:1, the mass ratio of PAPP / HDP was 3:1, and the mass ratio of PAPP / ADP was 4:1. The preparation method was the same as that of Example 1.

[0059] Table 1 Components of flame retardant polypropylene composition

[0060]

[0061] Comparative Example 1: a blank comparative example, that is, pure polypropylene; the difference from Example 1 is that no intumescent flame retardant, zinc-nickel bimetallic oxide catalyst, flame retardant additive and compatibilizer are added.

[0062] Comparative Example 2: The difference from Example 1 is that no zinc-nickel bimetallic oxide catalyst Zn 0.7 Ni 0.3 O, i.e., Zn 0.7 Ni 0.3 The dosage of O is 0; the rest is the same as in Example 1.

[0063] Comparative Example 3: The difference from Example 1 is that the zinc-nickel bimetallic oxide catalyst Zn 0.7 Ni 0.3 O was replaced with ZnO / NiO of equal weight; the rest was the same as in Example 1.

[0064] ZnO and NiO are mixed according to a mass ratio of Zn:Ni=7:3 to obtain the corresponding ZnO / NiO.

[0065] Comparative Example 4: The difference from Example 1 is that the zinc-nickel bimetallic oxide catalyst Zn 0.7 Ni 0.3 O was replaced with an equal amount of ZnO; the rest was the same as in Example 1.

[0066] Comparative Example 5: The difference from Example 1 is that the zinc-nickel bimetallic oxide catalyst Zn 0.7 Ni 0.3 O was replaced with an equal amount of NiO; the rest was the same as in Example 1.

[0067] Comparative Example 6: The difference from Example 1 is that the zinc-nickel bimetallic oxide catalyst Zn 0.7 Ni 0.3 O is replaced with an equal amount of Zn 0.4 Ni 0.6 O; the rest is the same as Example 1.

[0068] Comparative Example 7: The difference from Example 1 is that the zinc-nickel bimetallic oxide catalyst Zn0.7 Ni 0.3 O is replaced with an equal amount of Zn 0.5 Ni 0.5 O; the rest is the same as Example 1.

[0069] Comparative Example 8: The difference from Example 1 is that the zinc-nickel bimetallic oxide catalyst Zn 0.7 Ni 0.3 O is replaced with an equal amount of Zn 0.6 Ni 0.4 O; the rest is the same as Example 1.

[0070] Comparative Example 9: The difference from Example 1 is that the flame retardant additive NOR 116 is not added; the rest is the same as Example 1.

[0071] Comparative Example 10: The difference from Example 4 is that the flame retardant additive GW-540 is not added; the rest is the same as Example 4.

[0072] Comparative Example 11: The difference from Example 1 is that the amount of the flame retardant additive NOR 116 is increased from 0.1 part to 0.6 part; the rest is the same as Example 1.

[0073] Comparative Example 12: The difference from Example 4 is that the amount of flame retardant additive GW-540 is increased from 0.2 parts to 0.6 parts; the rest is the same as Example 4.

[0074] Comparative Example 13: The difference from Example 4 is that the flame retardant additive GW-540 is replaced with the commonly used light stabilizer UV-770 on the market; the rest is the same as Example 4.

[0075] Comparative Example 14: The difference from Example 1 is that the intumescent flame retardant PAPP / MPP is replaced with an equal amount of inorganic flame retardant magnesium hydroxide; the rest is the same as Example 1.

[0076] Comparative Example 15: This example differs from Example 1 in that the intumescent flame retardant PAPP / MPP is replaced with an equivalent PAPP / APP system. Specifically, the secondary flame retardant in Example 1 is replaced with ammonium polyphosphate (APP) instead of melamine polyphosphate (MPP). The remainder of the process is identical to Example 1.

[0077] Comparative Example 16: The difference from Example 1 is that the mass ratio of PAPP / MPP is changed from "2:1" to "1:1", and the rest is the same as Example 1.

[0078] Experimental and performance evaluation of polypropylene composites

[0079] 1. Flame retardant performance test conditions and standards are as follows:

[0080] UL-94 vertical burning specimen size: 130 × 13 × 3.2 mm 3 Test standard: ASTM D3801;

[0081] LOI specimen size: 100 × 6.5 × 3.2 mm 3 Test standard: ASTM 2863;

[0082] Peak burning rate (pk-HRR) and total heat of combustion (THR) are the most representative parameters of the flame retardancy of the material in the cone calorimetry test. The higher the pk-HRR and THR values, the more flammable the material is and the higher the fire risk. The test specimen size is: 100 × 100 × 3.2 mm 3 , the test standard is: ISO 5660.

[0083] 2. Mechanical properties test conditions and standards are as follows:

[0084] The specimen size of the tensile properties is 2 mm × 35 mm × 0.8 mm, the tensile rate is 20 mm / min, and the test standard is ASTM D882.

[0085] The specimen size for bending performance is 80 mm × 10 mm × 4 mm, and the test standard is GB / T 1040.1-2006.

[0086] The notched impact test specimen size is 80 mm × 10 mm × 4 mm, and a 1 J pendulum is used for impact testing. The test standard is ISO179-1:98.

[0087] The results are shown in Table 2 below.

[0088] Table 2 Flame retardant properties and mechanical properties

[0089]

[0090] From the test results in Table 2, it can be found that pure polypropylene has no flame retardant rating, while Examples 1 to 11 of the present invention all pass the UL-94 V0 rating test. The limiting oxygen index also increases from 17.8 vol% of pure polypropylene to over 30 vol%, transforming the flammable material into a flame-retardant material, and the flame retardant performance is greatly improved.

[0091] From the comparison between Comparative Example 2 and Example 1, it can be seen that when no zinc-nickel bimetallic oxide catalyst Zn 0.7 Ni 0.3 O, the carbonization ability of the specimen is too weak to protect the substrate to achieve the heat insulation effect, so that it burns to the fixture during the second ignition and has no flame retardant grade.0.7 Ni 0.3 After replacing ZnO with a ZnO / NiO mixture of the same mass ratio (Comparative Example 3), there is still no flame retardant grade, indicating that the catalytic carbonization ability of the ZnO / NiO mixture on the spline by simple blending is very weak, so that it cannot improve the flame retardant effect. The zinc-nickel bimetallic oxide catalyst obtained by the co-precipitation method of the present invention can greatly improve the catalytic carbonization effect on the spline, thereby enhancing the flame retardant properties of the polypropylene composite material. Furthermore, by comparing Comparative Example 4 and Comparative Example 5 with Example 1, it is found that the polypropylene composite material obtained by using ZnO or NiO alone still has no flame retardant grade. By comparing Comparative Example 6, Comparative Example 7, Comparative Example 8 with Example 1, it can be seen that the mass ratio of zinc and nickel is also a key factor. Only when the zinc content is between 70% and 90%, there is an obvious flame retardant effect and reaches the V0 grade. Among them, from Examples 1, 2 and 3, the catalyst used in Example 2 is Zn 0.8 Ni 0.2 O, that is, when the mass ratio of zinc to nickel is 8:2, the flame retardant properties of the splines are higher than those of Zn 0.7 Ni 0.3 O and Zn 0.9 Ni 0.1 O corresponds to the performance of the spline, which is the optimal ratio of zinc and nickel.

[0092] From Comparative Examples 9 and 10, it was found that when no flame retardant additive was added, the spline also had no flame retardant grade. The addition of flame retardant additives buys time for the catalytic carbonization of the catalyst, so the flame retardant effect is significantly improved. Furthermore, through Comparative Examples 11 and 12, it was found that when the addition amount of flame retardant additives (NOR 116 or GW-540) exceeds 0.5 parts, it can only reach V2 grade. This is because NOR 116 and GW-540 can not only capture active free radicals, but also act as initiators to promote the degradation of polypropylene. When the addition amount of flame retardant additives (NOR 116 or GW-540) is low, they mainly play the role of quenching free radicals and exert a flame retardant effect. However, when the addition amount is too high, they mainly act as initiators, promoting the degradation of polypropylene, resulting in the generation of molten droplets and igniting the absorbent cotton. Comparative Example 13 shows that not all light stabilizers have this flame retardant effect. The addition of light stabilizers NOR 116 and GW-540 significantly improves the flame retardant effect of polypropylene because their decomposition temperatures match that of polypropylene and they both have excellent vapor phase flame retardant effects.

[0093] From the comparison between Comparative Example 14 and Example 1, it can be seen that after replacing the intumescent flame retardant PAPP / MPP with an equal amount of inorganic flame retardant magnesium hydroxide, the specimen has no flame retardant grade and the heat release rate increases to 525 KW / m 2, the flame retardant performance is greatly reduced. This is because magnesium hydroxide needs to be added in an amount of more than 40% to have a significant flame retardant effect.

[0094] Comparative Examples 15 and 16 both showed no flame retardancy.

[0095] In summary, the present invention provides a flame-retardant polypropylene with excellent comprehensive performance and a preparation method thereof, and also provides a broader space for the application of polypropylene.

[0096] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above examples and is subject to numerous variations. All variations that can be directly derived or conceived by a person of ordinary skill in the art from the disclosure of the present invention are considered to be within the scope of protection of the present invention.

Claims

1. Flame retardant polypropylene composite material, characterized by: According to parts by weight, it is composed of 80-85 parts of polypropylene, 14.5-18.7 parts of intumescent flame retardant, 0.2-0.5 parts of catalyst, 0.1-0.5 parts of flame retardant additive and 0.1-0.5 parts of compatibilizer; The flame retardant additive is NOR 116 or GW-540; The catalyst is a zinc-nickel bimetallic oxide catalyst, and the zinc-nickel bimetallic oxide catalyst is Zn x Ni y O, x is any value between 0.7 and 0.9, y is any value between 0.1 and 0.3; and x + y = 1; The intumescent flame retardant is composed of a primary flame retardant and a secondary flame retardant, with the mass ratio of primary flame retardant to secondary flame retardant being 2 to 4:

1. The main flame retardant is piperazine pyrophosphate, and the secondary flame retardant is any one of melamine polyphosphate, aluminum hypophosphite, and aluminum diethylphosphinate; The preparation method of the zinc-nickel bimetallic oxide catalyst is: Dissolving zinc nitrate hexahydrate and nickel nitrate hexahydrate in distilled water under stirring to obtain a bimetallic solution; the mass ratio of zinc in the zinc nitrate hexahydrate to nickel in the nickel nitrate hexahydrate is 7-9:1-3; The bimetallic solution was reacted at 80±10°C for 2±0.5 h under stirring, and the pH of the reaction system was controlled to be 8-9 during the reaction. After the reaction is completed, the mixture is aged at 80±10°C for 1±0.2h and then filtered. The filter cake is washed with deionized water and then dried. The mixture is then calcined at 450-550°C for 3.5-4.5h and ground to obtain a zinc-nickel bimetallic oxide catalyst.

2. The flame-retardant polypropylene composite material according to claim 1, characterized in that: x is 0.8 and y is 0.

2.

3. The flame retardant polypropylene composite material according to claim 2, characterized in that: The compatibilizer is maleic anhydride grafted polypropylene or maleic anhydride grafted polyethylene.

4. The method for preparing the flame retardant polypropylene composite material according to any one of claims 1 to 3, wherein The following steps are involved: (1) Weigh polypropylene, intumescent flame retardant, catalyst, flame retardant additive and compatibilizer according to weight, and premix them in a mixer at 80±10°C for 5±1 min; the premixing speed is 300±50 r / min; (2) The mixed material obtained in step (1) is melted and sheared by a twin-screw extruder, and then extruded into granules. The extrusion temperature is 165-210°C, the rotation speed is 450±50 r / min, and the feed speed is 30±3 r / min.

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