A flame retardant for polycarbonate, a flame retardant polycarbonate and a method for producing the same

Abstract

The application discloses a kind of flame retardant for polycarbonate, flame-retardant polycarbonate and its preparation method, the flame retardant includes the following raw materials: modified nanometer montmorillonite 10-15 parts, modified nanometer aluminum hydroxide 5-10 parts, lignin 5-10 parts, ammonium polyphosphate and / or melamine phosphate 8-12 parts, phenyl silicone resin 5-10 parts and anti-dripping agent 0.2-0.3 parts.The application makes full use of the abundant source, low-cost montmorillonite, has obvious environmental protection value, can greatly reduce the production cost of flame-retardant polycarbonate;The carbon residue rate, heat resistance, smoke suppression and other properties of polycarbonate material are also improved.

Description

Technical Field

[0001] This invention relates to the field of flame retardant technology, specifically to a flame retardant for polycarbonate, flame-retardant polycarbonate, and a method for preparing the same. Background Technology

[0002] Due to its excellent overall performance, ease of processing, and low price, polycarbonate is widely used in electronics, automotive, and other industries. However, because it is rich in hydrocarbons, polycarbonate produces black or dense smoke when burning, and molten material drips, which can further escalate a fire. Therefore, combining low-cost, environmentally friendly flame-retardant materials with polymers such as polycarbonate to create composite flame-retardant materials shows promising potential. Different base materials require different flame retardants. Base materials with low limiting oxygen index require flame retardants with better flame retardant and smoke-suppressing effects. Base materials with relatively high limiting oxygen index can use appropriate flame retardant systems. Some existing flame-retardant materials suffer from high synthesis costs, a reliance on petroleum-derived products, complex compositions (such as some compound organic flame retardants), and less than ideal environmental sustainability. Some inorganic flame retardants offer good flame retardant effects, but their large dosage (30-50%) complicates the processing and significantly impacts the material's physical and mechanical properties.

[0003] Chinese patent CN201611128268.9 describes the preparation of flame-retardant polyurethane foam by compounding expandable graphite, fly ash, polyether polyol, and isocyanate, and adding a foaming agent and polydimethylsiloxane and / or silicone oil as foam stabilizers. Based on the total weight of the flame-retardant polyurethane foam, the foam contains 29-43% by weight of flame retardant (expandable graphite and fly ash) and 57-71% by weight of polyurethane. In this design, the flame retardant is an inorganic flame retardant and is used in large quantities. Chinese patent CN101948581B discloses an intumescent flame-retardant polyethylene containing organosilicon compounds. This intumescent flame-retardant polyethylene also contains a metal oxide hydrate containing organosilicon flame-retardant synergists. The content of each component by weight percentage is as follows: polyethylene 70-80%, compounded intumescent flame retardant 17-29.5%, and metal oxide hydrate containing organosilicon flame-retardant synergists 0.5-3%. This method is complex to prepare, and the flame-retardant effect needs improvement. Chinese patent CN202011557879.1 discloses a method for preparing flame-retardant polycarbonate. It uses polycarbonate, SAN, ASA powder, phosphazene flame retardants, triazine UV absorbers, benzotriazole weathering agents, hindered amine weathering agents, anti-dripping agents, colorants, antioxidants, metal passivators, and other processing aids to prepare the flame-retardant polycarbonate. Its main purpose is to obtain better UVC radiation resistance and effectively prevent the material from aging and yellowing. The improvement in flame retardant performance is relatively small. Chinese patent CN108824018A involves plasma activation treatment of montmorillonite, followed by organic modification with the addition of hexadecyltrimethylammonium bromide. The organically modified montmorillonite, phytic acid-modified chitosan powder, phenolic resin, and a flame retardant mixture are then mixed with asphalt raw materials to obtain a coating material. This coating material is then applied to a polyester substrate to obtain a flame-retardant and smoke-suppressing asphalt waterproof membrane. However, this method does not specify the exact flame retardant effect. Chinese patent CN106349664A discloses a flame-retardant polyhydroxyalkanoate composite material, comprising 5-30% phosphorus-based flame retardant, 5-20% nitrogen-containing flame retardant, 5-20% biomass carbon source, with the remainder being polyhydroxyalkanoate resin. This method uses a relatively large amount of flame-retardant components, and the flame-retardant effect needs further improvement. Chinese patent CN106009585A discloses a halogen-free flame-retardant polycarbonate material, comprising 70%–90% polycarbonate; 5%–10% other resins; 6%–15% halogen-free flame retardant; 5%–15% surface modifier; 3%–10% toughening agent; 0.6%–2.5% antioxidant; 0.4%–2.5% lubricant; and 0.3%–1.2% weather resistant agent. The provided halogen-free flame-retardant polycarbonate material uses halogen-free flame retardants, especially organosilicon-based flame retardants, as the flame-retardant component. However, this method has a relatively poor flame-retardant effect. Summary of the Invention

[0004] The purpose of this invention is to provide a flame retardant for polycarbonate, so as to solve the defect that the flame retardant effect of existing flame retardants needs to be improved.

[0005] Another objective of this invention is to provide a flame-retardant polycarbonate.

[0006] Another objective of this invention is to provide a method for preparing flame-retardant polycarbonate.

[0007] To achieve the above objectives, the present invention provides a flame retardant for polycarbonate, comprising, by weight parts: 10-15 parts modified nano-montmorillonite, 5-10 parts modified nano-aluminum hydroxide, 5-10 parts lignin, 8-12 parts ammonium polyphosphate and / or melamine phosphate, 5-10 parts phenyl silicone resin, and 0.2-0.3 parts anti-dripping agent.

[0008] The anti-dripping agent is a commonly used anti-dripping agent in the art, and its type is not particularly limited; for example, it can be modified polytetrafluoroethylene. The phenyl silicone resin mentioned in this invention can be methylphenyl silicone resin, vinylphenyl silicone resin, epoxyphenyl silicone resin, or other modified phenyl silicone resins, which can be commercially available or synthesized by ordinary synthetic methods; the polycarbonate mentioned in this invention can be aliphatic polycarbonate or aromatic polycarbonate, which can be commercially available or synthesized by ordinary synthetic methods.

[0009] The modified nano-montmorillonite used in the flame retardant for polycarbonate of the present invention is prepared by the following method:

[0010] Nano-montmorillonite was activated by plasma treatment with gas. After activation, the nano-montmorillonite was dispersed in deionized water, and then a silane coupling agent was added and mixed evenly. After filtration, washing and drying, modified nano-montmorillonite was obtained.

[0011] The method for preparing the modified nano-aluminum hydroxide is as follows:

[0012] Nano-aluminum hydroxide was subjected to plasma activation treatment. After activation, the nano-aluminum hydroxide was dispersed in deionized water, and then a silane coupling agent was added and mixed evenly. After filtration, washing and drying, modified nano-montmorillonite was obtained.

[0013] The flame retardant for polycarbonate described in this invention uses one or more of the following gases during plasma activation: oxygen, air, carbon dioxide, nitrogen, and argon.

[0014] The flame retardant for polycarbonate described in this invention is activated under the following plasma conditions: power of 30-100 watts, processing time of 10-50 minutes, and gas flow rate of 20-60 ml / min.

[0015] The flame retardant for polycarbonate described in this invention uses γ-(2,3-epoxypropoxy)propyltrimethoxysilane and / or 3-aminopropyltriethoxysilane as the silane coupling agent; the mass ratio of the silane coupling agent to nano-montmorillonite is 2-5:100, and the mass ratio of the silane coupling agent to nano-aluminum hydroxide is 2-5:100.

[0016] The flame retardant for polycarbonate described in this invention is prepared by adding a silane coupling agent at 65–85°C and homogenizing at a constant temperature for 2–4 hours.

[0017] To achieve the above objectives, the present invention also provides a flame-retardant polycarbonate comprising 33 to 58 parts by weight of the above-mentioned flame retardant, 90 to 140 parts by weight of polycarbonate base material, and 0.2 to 0.5 parts by weight of antioxidant.

[0018] The method for preparing flame-retardant polycarbonate according to the present invention involves mixing and extruding a flame retardant, a polycarbonate base material, and an antioxidant in a twin-screw extruder to obtain a polycarbonate composite material, and then subjecting the polycarbonate composite material to plasma activation treatment with gas to obtain a flame-retardant polycarbonate product.

[0019] The method for preparing flame-retardant polycarbonate according to the present invention, wherein the gas is one or more of methane, ethane, and butane; the plasma activation treatment conditions are 20-50 watts, the treatment time is 20-60 minutes, and the gas flow rate is 30-60 ml / min.

[0020] Beneficial effects of this invention:

[0021] A plasma reactor is used to activate nano-montmorillonite and nano-aluminum hydroxide using active particles such as electrons, free radicals, ions, and excited-state molecules in the plasma. This enriches the surface of the treated nano-montmorillonite and nano-aluminum hydroxide with active groups, increasing their surface energy and activity. This allows them to react better with other substances, promoting better bonding between the flame retardant and the polymer matrix material, thereby improving the flame retardant effect. The activated nano-montmorillonite or nano-aluminum hydroxide is then mixed with a silane coupling agent to further improve vertical combustion performance and oxygen index, reducing the rate and total amount of heat / smoke release during combustion. The flame retardant components of this invention include inorganic materials, such as modified montmorillonite and modified aluminum hydroxide, which improve the combustion performance of the material. Components such as lignin, melamine phosphate, and ammonium polyphosphate further improve the char formation properties of the material, preventing the spread of fire and the diffusion of flammable components. Phenyl silicone resin further improves the temperature resistance of the material. The composite of these materials improves the limiting oxygen index of polycarbonate materials. The entire process does not involve excessive chemical additions and leaves no solvent residue, making it simple and easy to implement.

[0022] This invention makes extensive use of montmorillonite, which is abundant and inexpensive, and has significant environmental value. It can greatly reduce the production cost of flame-retardant polycarbonate; the char residue rate, heat resistance, and smoke suppression properties of polycarbonate materials are also improved. Detailed Implementation

[0023] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0024] Test method:

[0025] Limiting Oxygen Index (LOI): The limiting oxygen index (LOI) was measured using an LOI meter (model 5801, manufactured by Kunshan Yangyi Testing Instruments Co., Ltd.) in accordance with standard GB / T 2406—2009.

[0026] In the following examples, all quantities are parts by weight.

[0027] Example 1

[0028] Step 1:

[0029] Preparation of modified nano-montmorillonite:

[0030] A plasma reactor was used, with oxygen as the treatment gas. Nano-montmorillonite was modified under conditions of 100 W reaction power, 50 min treatment time, and 40 ml / min gas flow rate. The plasma-treated nano-montmorillonite was then dispersed in deionized water by high-speed stirring. The temperature was then raised to 80 °C, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane (silane coupling agent 560) was slowly added while stirring. The mixture was stirred at 80 °C for 4 h, filtered, washed, dried, ground, and sieved to obtain organically modified montmorillonite. The mass ratio of silane coupling agent 560 to nano-montmorillonite was 3:100.

[0031] Preparation of modified nano-aluminum hydroxide:

[0032] A plasma reactor was used, with oxygen as the treatment gas. Nano-aluminum hydroxide was modified under conditions of 100 W reaction power, 50 min treatment time, and 40 ml / min gas flow rate. The plasma-treated nano-aluminum hydroxide was added to deionized water and dispersed by high-speed stirring. Then, while stirring, γ-(2,3-epoxypropoxy)propyltrimethoxysilane (silane coupling agent 560) was slowly added to 80 °C. The mixture was stirred at 80 °C for 4 h, filtered, washed, dried, ground, and sieved to obtain organically modified aluminum hydroxide. The mass ratio of silane coupling agent 560 to nano-aluminum hydroxide was 2.5:100.

[0033] Step 2:

[0034] Preparation of flame retardants:

[0035] 15 parts of modified nano-montmorillonite obtained in step 1 were mixed at high speed with 10 parts of ammonium polyphosphate, 10 parts of lignin, 8 parts of modified nano-aluminum hydroxide, 6 parts of methylphenyl silicone resin, and 0.2 parts of anti-dripping agent modified polytetrafluoroethylene to form a composite flame retardant material matrix.

[0036] Step 3:

[0037] Preparation of polycarbonate composite materials:

[0038] Take 30 parts of the flame-retardant material matrix obtained in step 2, 90 parts of polycarbonate base material (PC-122), and 0.3 parts of antioxidant (antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2) and add them to a twin-screw extruder at 275°C for mixing, extrusion and granulation to obtain a flame-retardant polycarbonate composite material.

[0039] Step 4:

[0040] Modification of polycarbonate composites:

[0041] The polycarbonate composite material obtained in step 3 was treated with ethane gas in a plasma reactor at a reaction power of 50 watts, a treatment time of 25 minutes, and a gas flow rate of 40 ml / min to obtain a flame-retardant polycarbonate product.

[0042] The limiting oxygen index (LOI) of flame-retardant polycarbonate products is 38.

[0043] Example 2

[0044] Step 1:

[0045] The preparation methods of modified nano-montmorillonite and modified nano-aluminum hydroxide are the same as in Example 1, except that nitrogen is used as the treatment gas; the reaction power is 50 watts, the treatment time is 40 minutes, the gas flow rate is 60 ml / min, and the silane coupling agent and nano-montmorillonite or nano-aluminum hydroxide are stirred at a constant temperature of 65°C for 2 hours.

[0046] Step 2:

[0047] 13 parts of modified nano-montmorillonite obtained in step 1 were mixed at high speed with 10 parts of ammonium polyphosphate, 8 parts of lignin, 10 parts of modified nano-aluminum hydroxide, 7 parts of vinyl phenyl silicone resin, and 0.3 parts of anti-dripping agent modified polytetrafluoroethylene to form a matrix for the compounded flame retardant material.

[0048] Step 3:

[0049] Preparation of polycarbonate composite materials:

[0050] Take 40 parts of the flame-retardant material matrix obtained in step 2, 120 parts of polycarbonate base material (PC-115), and 0.35 parts of antioxidant (antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2) and add them to a twin-screw extruder at 285°C for mixing, extrusion and granulation to obtain a flame-retardant polycarbonate composite material.

[0051] Step 4:

[0052] Same as Example 1, except that the gas being processed is butane, the reaction power is 50 watts, the processing time is 25 minutes, and the gas flow rate is 50 ml / min.

[0053] The limiting oxygen index (LOI) of the flame-retardant polycarbonate product is 39.

[0054] Example 3

[0055] Step 1:

[0056] The preparation methods of modified nano-montmorillonite and modified nano-aluminum hydroxide are the same as in Example 1, except that air is used as the treatment gas; the reaction power is 40 watts, the treatment time is 40 minutes, the gas flow rate is 20 ml / min, and the silane coupling agent and nano-montmorillonite or nano-aluminum hydroxide are stirred at a constant temperature of 70°C for 3 hours; the silane coupling agent is 3-aminopropyltriethoxysilane (silane coupling agent 550), and the mass ratio of silane coupling agent 550 to nano-aluminum hydroxide is 3:100.

[0057] Step 2:

[0058] Ten parts of the modified nano-montmorillonite obtained in step 1 were mixed at high speed with eight parts of ammonium polyphosphate, ten parts of lignin, nine parts of modified nano-aluminum hydroxide, six parts of methylphenyl silicone resin, and 0.2 parts of anti-dripping agent modified polytetrafluoroethylene to form the matrix of the compounded flame retardant material.

[0059] Step 3:

[0060] Preparation of polycarbonate composite materials:

[0061] Take 45 parts of the flame-retardant material matrix obtained in step 2, 110 parts of polycarbonate base material (PC-110), and 0.3 parts of antioxidant (antioxidant 1010 and antioxidant 626 in a mass ratio of 1:1) and add them to a twin-screw extruder at 290°C for mixing, extrusion and granulation to obtain a flame-retardant polycarbonate composite material.

[0062] Step 4:

[0063] Same as Example 1, except that the gas being processed is butane, the reaction power is 40 watts, the processing time is 25 minutes, and the gas flow rate is 40 ml / min.

[0064] The limiting oxygen index (LOI) of flame-retardant polycarbonate products is 40.

[0065] Example 4

[0066] Step 1:

[0067] The preparation methods of modified nano-montmorillonite and modified nano-aluminum hydroxide are the same as in Example 1, except that nitrogen is used as the treatment gas; the reaction power is 30 watts, the treatment time is 35 minutes, the gas flow rate is 40 ml / min; the silane coupling agent is 3-aminopropyltriethoxysilane (silane coupling agent 550), the mass ratio of silane coupling agent 550 to nano-montmorillonite is 2.5:100, and the mass ratio of silane coupling agent 550 to nano-aluminum hydroxide is 3:100.

[0068] Step 2:

[0069] 15 parts of modified nano-montmorillonite obtained in step 1 were mixed at high speed with 10 parts of melamine phosphate, 5 parts of lignin, 10 parts of modified nano-aluminum hydroxide, 10 parts of methylphenyl silicone resin, and 0.3 parts of anti-dripping agent modified polytetrafluoroethylene to form a composite flame retardant material matrix.

[0070] Step 3:

[0071] Preparation of polycarbonate composite materials:

[0072] Take 30 parts of the flame-retardant material matrix obtained in step 2, 130 parts of polycarbonate base material (PC-110L), and 0.5 parts of antioxidant (antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2) and add them to a twin-screw extruder at 295°C for mixing, extrusion and granulation to obtain a flame-retardant polycarbonate composite material.

[0073] Step 4:

[0074] Same as Example 1, except that the reaction power is 50 watts, the processing time is 30 minutes, and the gas flow rate is 40 ml / min.

[0075] The limiting oxygen index (LOI) of the flame-retardant polycarbonate product is 39.

[0076] Example 5

[0077] Step 1:

[0078] The preparation methods of modified nano-montmorillonite and modified nano-aluminum hydroxide are the same as in Example 1, except that argon is used as the treatment gas; the reaction power is 40 watts, the treatment time is 35 minutes, the gas flow rate is 40 ml / min; the mass ratio of silane coupling agent 560 to nano-montmorillonite is 3.5:100, and the mass ratio of silane coupling agent 560 to nano-aluminum hydroxide is 3:100.

[0079] Step 2:

[0080] 10 parts of modified nano-montmorillonite, 10 parts of melamine phosphate, 8 parts of lignin, 10 parts of modified nano-aluminum hydroxide, 5 parts of epoxy phenyl silicone resin, and 0.2 parts of anti-dripping agent modified polytetrafluoroethylene obtained in step 1 were mixed at high speed to form a matrix for the compounded flame retardant material.

[0081] Step 3:

[0082] Preparation of polycarbonate composite materials:

[0083] Take 30 parts of the flame-retardant material matrix obtained in step 2, 110 parts of polycarbonate base material (PC-115), and 0.2 parts of antioxidant (antioxidant 1010 and antioxidant 626 in a mass ratio of 1:1) and add them to a twin-screw extruder at 285°C for mixing, extrusion and granulation to obtain a flame-retardant polycarbonate composite material.

[0084] Step 4:

[0085] Same as Example 1, except that the gas being processed is methane, the reaction power is 40 watts, the processing time is 35 minutes, and the gas flow rate is 30 ml / min.

[0086] The limiting oxygen index (LOI) of the flame-retardant polycarbonate product is 39.

[0087] Example 6

[0088] Step 1:

[0089] The preparation methods of modified nano-montmorillonite and modified nano-aluminum hydroxide are the same as in Example 1, except that the reaction power is 50 watts, the processing time is 10 minutes, and the gas flow rate is 40 ml / min; the mass ratio of silane coupling agent 560 to nano-montmorillonite is 2:100, and the mass ratio of silane coupling agent 560 to nano-aluminum hydroxide is 5:100.

[0090] Step 2:

[0091] 12 parts of modified nano-montmorillonite obtained in step 1 were mixed at high speed with 10 parts of melamine phosphate, 5 parts of lignin, 8 parts of modified nano-aluminum hydroxide, 7 parts of methylphenyl silicone resin, and 0.2 parts of anti-dripping agent modified polytetrafluoroethylene to form a composite flame retardant material matrix.

[0092] Step 3:

[0093] Preparation of polycarbonate composite materials:

[0094] Take 30 parts of the flame-retardant material matrix obtained in step 2, 110 parts of polycarbonate base material (PC-115), and 0.35 parts of antioxidant (antioxidant 1076 and antioxidant 626 in a mass ratio of 1:2) and add them to a twin-screw extruder at 280°C for mixing, extrusion and granulation to obtain a flame-retardant polycarbonate composite material.

[0095] Step 4:

[0096] Same as Example 1, except that the reaction power is 30 watts, the processing time is 30 minutes, and the gas flow rate is 50 ml / min.

[0097] The limiting oxygen index (LOI) of the flame-retardant polycarbonate product is 39.

[0098] Example 7

[0099] Step 1:

[0100] The preparation methods of modified nano-montmorillonite and modified nano-aluminum hydroxide are the same as in Example 1, except that carbon dioxide is used as the treatment gas; the reaction power is 50 watts, the treatment time is 40 minutes, the gas flow rate is 35 ml / min; the silane coupling agent is silane coupling agent 550, the mass ratio of silane coupling agent 550 to nano-montmorillonite is 5:100, and the mass ratio of silane coupling agent 550 to nano-aluminum hydroxide is 2:100.

[0101] Step 2:

[0102] Ten parts of the modified nano-montmorillonite obtained in step 1 were mixed at high speed with 12 parts of melamine phosphate, 5 parts of lignin, 5 parts of modified nano-aluminum hydroxide, 6 parts of methylphenyl silicone resin, and 0.3 parts of anti-dripping agent modified polytetrafluoroethylene to form the matrix of the compounded flame retardant material.

[0103] Step 3:

[0104] Preparation of polycarbonate composite materials:

[0105] Take 30 parts of the flame-retardant material matrix obtained in step 2, 140 parts of polycarbonate base material (PC-15), and 0.3 parts of antioxidant (antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2) and add them to a twin-screw extruder at 290°C for mixing, extrusion and granulation to obtain a flame-retardant polycarbonate composite material.

[0106] Step 4:

[0107] Same as Example 1, except that the gas being processed is methane, the reaction power is 30 watts, the processing time is 40 minutes, and the gas flow rate is 30 ml / min.

[0108] The limiting oxygen index (LOI) of flame-retardant polycarbonate products is 40.

[0109] Comparative Example 1

[0110] Same as Example 7, except that phenyl silicone resin is not added in step 2.

[0111] The limiting oxygen index (LOI) of flame-retardant polycarbonate products is 34.

[0112] Comparative Example 2

[0113] Same as Example 7, except that the methylphenyl silicone resin in step 2 is replaced with propyltrimethoxysilane.

[0114] The limiting oxygen index (LOI) of flame-retardant polycarbonate products is 35.

[0115] Comparative Example 3

[0116] Same as Example 7, except that modified nano-montmorillonite is not added in step 2. The raw material composition is 12 parts of melamine phosphate, 5 parts of lignin, 15 parts of modified nano-aluminum hydroxide, 6 parts of methyl phenyl silicone resin, and 0.3 parts of anti-dripping agent modified polytetrafluoroethylene.

[0117] The limiting oxygen index (LOI) of flame-retardant polycarbonate products is 31.

[0118] Comparative Example 4

[0119] Same as Example 7, except that the modified nano-aluminum hydroxide in step 2 is replaced with unmodified nano-aluminum hydroxide.

[0120] The limiting oxygen index (LOI) of flame-retardant polycarbonate products is 32.

[0121] Comparative Example 5

[0122] Same as Example 7, except that step 4 of the modification process is not performed.

[0123] The limiting oxygen index (LOI) of flame-retardant polycarbonate products is 30.

[0124] Comparative Example 6

[0125] Same as Example 7, except that melamine phosphate in step 2 is replaced with triphenyl phosphate.

[0126] The limiting oxygen index (LOI) of flame-retardant polycarbonate products is 29.

[0127] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A flame retardant for polycarbonate, characterized in that, The product comprises, by weight parts, the following raw materials: 10-15 parts modified nano montmorillonite, 5-10 parts modified nano aluminum hydroxide, 5-10 parts lignin, 8-12 parts ammonium polyphosphate and / or melamine phosphate, 5-10 parts phenyl silicone resin, and 0.2-0.3 parts anti-drip agent. The preparation method of the modified nano-montmorillonite is as follows: Nano-montmorillonite was activated by plasma treatment with gas. After activation, the nano-montmorillonite was dispersed in deionized water, and then a silane coupling agent was added and mixed evenly. After filtration, washing and drying, modified nano-montmorillonite was obtained. The preparation method of the modified nano-aluminum hydroxide is as follows: Nano-aluminum hydroxide was subjected to plasma activation treatment. After activation, the nano-aluminum hydroxide was dispersed in deionized water, and then a silane coupling agent was added and mixed evenly. After filtration, washing and drying, modified nano-aluminum hydroxide was obtained.

2. The flame retardant for polycarbonate according to claim 1, characterized in that, During plasma activation, the processing gas is one or more of oxygen, air, carbon dioxide, nitrogen, and argon.

3. The flame retardant for polycarbonate according to claim 1, characterized in that, The plasma activation conditions are a power of 30-100 watts, a processing time of 10-50 minutes, and a gas flow rate of 20-60 ml / min.

4. The flame retardant for polycarbonate according to claim 1, characterized in that, The silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane and / or 3-aminopropyltriethoxysilane. The mass ratio of the silane coupling agent to nano-montmorillonite is 2~5:100, and the mass ratio of the silane coupling agent to aluminum hydroxide is 2~5:

100.

5. The flame retardant for polycarbonate according to claim 1, characterized in that, Add silane coupling agent at 65~85℃ and homogenize at a constant temperature for 2~4 h.

6. A flame-retardant polycarbonate, characterized in that, It comprises 30 to 45 parts by weight of the flame retardant as described in any one of claims 1 to 5, 90 to 140 parts by weight of the polycarbonate base material, and 0.2 to 0.5 parts by weight of the antioxidant.

7. The method for preparing the flame-retardant polycarbonate according to claim 6, characterized in that, Flame retardant, polycarbonate base material and antioxidant are mixed and extruded in a twin-screw extruder to obtain a polycarbonate composite material. The polycarbonate composite material is then subjected to plasma activation treatment with gas to obtain a flame-retardant polycarbonate product.

8. The method for preparing flame-retardant polycarbonate according to claim 7, characterized in that, The gas is one or more of methane, ethane, and butane; the plasma activation treatment conditions are 20-50 watts, the treatment time is 20-60 minutes, and the gas flow rate is 30-60 ml / min.