Composite flame retardant, preparation method thereof and application of composite flame retardant in preparation of flame-retardant recycled plastic

Abstract

The invention belongs to the technical field of recycled plastics, and particularly relates to a composite flame retardant, a preparation method thereof and application of the composite flame retardant in preparation of flame-retardant recycled plastics. The composite flame retardant is prepared from the following raw materials: ammonium polyphosphate, 2, 3-dimethyl-2, 3-diphenyl butane and a flame-retardant PP recycled material, the mass ratio of the ammonium polyphosphate to the 2, 3-dimethyl-2, 3-diphenyl butane to the flame-retardant PP recycled material is (1-3): (0.5-1.5): (6-8); the problems that products with high mechanical properties cannot be manufactured by directly recycling waste PP, and the products are poor in flame retardant property, poor in flowability and the like are solved, and the provided product has good elongation at break, impact property and flame retardant property and relatively high melt index.

Description

Technical Field

[0001] The invention belongs to the technical field of recycled plastics, and in particular relates to a composite flame retardant and a preparation method thereof and application in the preparation of flame-retardant recycled plastics. Background Art

[0002] PP (polypropylene) has excellent chemical resistance, heat resistance, and mechanical properties, and is widely used in home appliances, automobiles, food packaging, medical devices, aerospace, etc. With the surge in the use of PP, it has become a waste polymer material with a large output in recent years, exacerbating "white pollution" and causing a waste of resources.

[0003] At present, the main treatment methods for waste PP are landfill, incineration, recycling, etc. However, for landfill of waste PP, the degradation of waste PP is very slow, and it takes about 20-30 years to completely decompose; for incineration of waste PP, the dioxins and other toxic gases produced will seriously pollute the air. Both landfill and incineration pose a serious threat to the environment, so recycling of waste PP is of great significance.

[0004] As people's living standards improve, home appliances are replaced more and more frequently, and the demand for PP materials used in home appliances is also increasing. However, the price of PP virgin materials is higher than that of recycled waste PP materials, resulting in high production costs for home appliances. Therefore, applying waste PP to home appliances can reduce the production costs of home appliances while also realizing the resource utilization of waste PP.

[0005] However, since PP is affected by factors such as light, heat, oxygen and external force during use, its molecular structure will change and its mechanical properties will significantly deteriorate. Direct recycling cannot produce products that require high mechanical properties.

[0006] A Chinese patent with publication number CN101798423A discloses a modified composite material using waste polypropylene plastic parts as raw materials and a preparation method thereof. The modified composite material is composed of the following components by weight percentage: 0-95% virgin polypropylene, 5%-100% recycled PP, 0-60% filler, 0-20% toughening agent, 0-1.5% coupling agent, 0-1% heat stabilizer, 0-1% light stabilizer, 0-1% processing aid and 0-1% nucleating agent. The modified composite material can be used for automotive parts, home appliances, turnover boxes, floor panels, pipes, etc.

[0007] The Chinese patent with publication number CN115521535B discloses a high-impact recycled polypropylene resin material and its preparation method; including: 64-84 parts of recycled PP containing mineral filler, 15-30 parts of lignin, 1-5 parts of polypropylene-maleic anhydride copolymer, 1-2 parts of silane coupling agent, 0.1-1 parts of light stabilizer, 0.1-1 parts of antioxidant, and 0.2-2 parts of lubricant. The polypropylene material obtained by this technical solution has stable performance and excellent impact resistance, and can be widely used in products such as small household appliance shells, and has broad application market prospects.

[0008] However, the above technical solutions do not pay attention to the flame retardant properties of materials prepared from recycled plastics. If a short circuit, overheating or other failure occurs in a home appliance, it may cause the electrical components to catch fire. If these home appliance materials do not have flame retardant properties, the fire may spread rapidly, increasing the severity of the fire. In addition to not paying attention to flame retardant properties, the existing materials prepared from recycled plastics have poor fluidity, resulting in production difficulties and increased production costs. For example, the melt flow rate of the recycled polypropylene resin material obtained in the Chinese patent with publication number CN115521535B is 13.5-16.1g / 10min. Summary of the invention

[0009] In view of the problems that existing waste PP cannot be directly recycled to produce products with high mechanical properties, and the products have poor flame retardancy and poor fluidity, the present invention provides a composite flame retardant and a preparation method thereof, and an application in the preparation of flame retardant recycled plastics. The flame retardant recycled PP provided by the present invention has good elongation at break, impact resistance, flame retardancy and a high melt index.

[0010] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0011] The first aspect of the present invention provides a composite flame retardant, comprising raw materials including ammonium polyphosphate, 2, 3-dimethyl-2, 3-diphenylbutane and flame-retardant PP recycled material; the mass ratio of the ammonium polyphosphate, 2, 3-dimethyl-2, 3-diphenylbutane and flame-retardant PP recycled material is 1-3:0.5-1.5:6-8.

[0012] As some preferred embodiments, the flame retardant PP recycled material has a melt index of 2-4 g / 10 min (2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min, 3.5 g / 10 min, 4 g / 10 min) at 230 ° C and 2.16 kg, and a notched impact strength of 4-8 kJ / m 2 (4 kJ / m 2 4.5kJ / m 2 , 5kJ / m 2 , 5.5kJ / m 2 , 6kJ / m2 、6.5kJ / m 2 , 7kJ / m 2 , 7.5kJ / m 2 , 8kJ / m 2 ), specific gravity is 0.99-1.05g / cm 3 (0.99 g / cm 3 , 1.0g / cm 3 , 1.01g / cm 3 , 1.02g / cm 3 ).

[0013] As a preferred embodiment, the flame retardant PP recycled material has a melt index of 3 kJ / m at 230°C and 2.16 kg. 2 , notched impact strength is 6kJ / m 2 , specific gravity is 1.02g / cm 3 .

[0014] The second aspect of the present invention provides a method for preparing the composite flame retardant, which comprises uniformly mixing ammonium polyphosphate, 2,3-dimethyl-2,3-diphenylbutane and flame-retardant PP recycled material to obtain the composite flame retardant.

[0015] The third aspect of the present invention provides the use of the above-mentioned composite flame retardant in the preparation of flame-retardant recycled plastics.

[0016] The fourth aspect of the present invention provides a flame retardant recycled PP. The raw materials include, by mass: 50-70 parts of PP mixed color PP recycled materials, 5-15 parts of PP paint barrel recycled materials, 5-15 parts of PP washing machine recycled materials, 10-30 parts of PP multi-color cup recycled materials, 1-5 parts of the above-mentioned composite flame retardant, 0.2-1 parts of antioxidants, 0.5-1 parts of lubricants, and 0.01-0.25 parts of color powder.

[0017] As some preferred embodiments, the PP heterochromatic recycled material has a melt index of 10-20 g / 10 min (10 g / 10 min, 12 g / 10 min, 14 g / 10 min, 15 g / 10 min, 16 g / 10 min, 18 g / 10 min, 20 g / 10 min) at 230 ° C and 2.16 kg, and a notched impact strength of 4-5 kJ / m 2 (4 kJ / m 2 4.2kJ / m 2 4.4kJ / m 2 4.5kJ / m 2 4.6kJ / m 2 4.8kJ / m 2 , 5.0kJ / m 2), specific gravity is 0.93-0.95g / cm 3 (A few examples include 0.93 g / cm 3 、0.94g / cm 3 , 0.95g / cm 3 ).

[0018] The melt index is tested according to GB / T 3682.12018; the notched impact strength is tested according to GB / T1843-2008; and the specific gravity is tested according to the liquid pycnometer method of GB / T 1033.1-2008.

[0019] As a preferred embodiment, the PP heterochromatic recycled material has a melt index of 15 g / 10 min at 230° C. and 2.16 kg, and a notched impact strength of 4.5 kJ / m 2 , specific gravity is 0.94g / cm 3 .

[0020] As some preferred embodiments, the PP paint barrel recycled material has a melt index of 3-5g / 10min (3g / 10min, 3.5g / 10min, 4g / 10min, 4.5g / 10min, 5g / 10min) at 230°C and 2.16Kg, and a notched impact strength of 10-20kJ / m 2 (A few examples include 10 kJ / m 2 、12kJ / m 2 、14kJ / m 2 、15kJ / m 2 、16kJ / m 2 、18kJ / m 2 、20kJ / m 2 ), specific gravity is 0.93-0.95g / cm 3 (A few examples include 0.93 g / cm 3 、0.94g / cm 3 , 0.95g / cm 3 ).

[0021] As a preferred embodiment, the melt index of the PP paint barrel recycled material at 230°C and 2.16Kg is 3g / 10min, and the notched impact strength is 15kJ / m 2 , specific gravity is 0.95g / cm 3 .

[0022] As some preferred embodiments, the PP washing machine recycled material has a melt index of 25-35 g / 10 min (25 g / 10 min, 28 g / 10 min, 30 g / 10 min, 32 g / 10 min, 35 g / 10 min) at 230 ° C and 2.16 kg, and a notched impact strength of 4-6 kJ / m 2 (4 kJ / m 2 4.2kJ / m 2 4.5kJ / m 2 4.5kJ / m 2 4.6kJ / m 2 4.8kJ / m 2 , 5kJ / m 2 ), specific gravity is 0.93-0.96g / cm 3 (A few examples include 0.93 g / cm 3 、0.94g / cm 3 , 0.95g / cm 3 , 0.96g / cm 3 ).

[0023] As a preferred embodiment, the PP washing machine recycled material has a melt index of 30 g / 10 min and a notched impact strength of 6 kJ / m at 230°C and 2.16 kg. 2 , specific gravity is 0.96g / cm 3 .

[0024] As some preferred embodiments, the PP multi-color cup recycled material has a melt index of 10-20 g / 10 min (10 g / 10 min, 12 g / 10 min, 14 g / 10 min, 15 g / 10 min, 16 g / 10 min, 18 g / 10 min, 20 g / 10 min) at 230 ° C and 2.16 kg, and a notched impact strength of 4-6 kJ / m 2 (4 kJ / m 2 4.2kJ / m 2 4.5kJ / m 2 4.5kJ / m 2 4.6kJ / m 2 4.8kJ / m 2 , 5kJ / m 2 ), specific gravity is 0.93-0.95g / cm 3 (A few examples include 0.93 g / cm 3 、0.94g / cm 3 , 0.95g / cm 3 ).

[0025] As a preferred embodiment, the PP multi-color cup recycled material has a melt index of 15g / 10min and a notched impact strength of 5kJ / m at 230°C and 2.16Kg. 2 , specific gravity is 0.93g / cm 3 .

[0026] As some preferred implementations, the antioxidant is a mixture of 2,6-tert-butyl-4-methylphenol and bis(3,5-tert-butyl-4-hydroxyphenyl)sulfide, and the mass ratio of the two is 0.1-0.5:0.1-0.5.

[0027] As some preferred implementations, the lubricant is selected from one or more of polyethylene wax, ethylene bisstearamide, zinc stearate, and calcium stearate, preferably polyethylene wax.

[0028] The present invention does not specifically limit the toner, and includes but is not limited to titanium dioxide, iron red, phthalocyanine red, cobalt titanium green or phthalocyanine green, ultramarine blue, phthalocyanine blue, titanium yellow, and azo yellow.

[0029] The fifth aspect of the present invention provides a method for preparing the above-mentioned flame-retardant recycled PP, comprising the following steps: mixing PP mixed color recycled material, PP paint barrel recycled material, PP washing machine recycled material, PP multi-color cup recycled material, composite flame retardant and lubricant for a first granulation to obtain primary granules; mixing the primary granules, antioxidant and color powder for a second granulation to obtain flame-retardant recycled PP.

[0030] As some preferred embodiments, the primary granulation and the secondary granulation are both carried out in a melt extruder.

[0031] As some preferred embodiments, the temperatures of each zone of the melt extruder are: the temperature of zone one is 190-200°C (190°C, 195°C, 200°C can be listed), the temperature of zone two is 195-205°C (195°C, 200°C, 205°C can be listed), the temperature of zone three is 220-240°C (220°C, 230°C, 240°C can be listed), the temperature of zone four is 220-240°C (220°C, 230°C, 240°C can be listed), the temperature of zone five is 190-210°C (190°C, 200°C, 210°C can be listed), and the temperature of zone six is ​​180-200°C (180°C, 190°C, 200°C can be listed).

[0032] As a preferred embodiment, the temperatures of each zone of the melt extruder are: zone one temperature is 195°C, zone two temperature is 200°C, zone three temperature is 230°C, zone four temperature is 230°C, zone five temperature is 200°C, and zone six temperature is 190°C.

[0033] As some preferred implementation modes, the screw speed of the melt extruder is 30-40 r / min, preferably 36 r / min.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The present invention improves the flame retardant properties of flame retardant recycled PP through a specific composite flame retardant.

[0036] (2) The present invention improves the impact performance and elongation at break of flame-retardant recycled PP by using specific recycled PP, especially recycled paint bucket material.

[0037] (3) The present invention improves the flame retardant properties of flame retardant recycled PP by adopting secondary granulation.

[0038] (4) The present invention improves the melt index and flame retardant properties of flame retardant recycled PP by adopting specific temperatures in each zone of the melt extruder. DETAILED DESCRIPTION

[0039] The present invention is further explained below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0040] In the following examples, unless otherwise specified, all raw materials used were commercially available or prepared by conventional methods in the art.

[0041] The sources of the recycled materials involved in the examples and comparative examples of the present invention are not specifically limited.

[0042] The recycled materials involved in Application Examples 1-5 of the present invention and Comparative Application Examples 1-3 are:

[0043] PP mixed color acrylic recycled material is PP mixed color acrylic crushed material with a melt index of 15g / 10min at 230℃ and 2.16Kg, and a notched impact strength of 4.5kJ / m 2 , specific gravity is 0.94g / cm 3 ;

[0044] PP paint barrel recycled material, the melt index at 230℃, 2.16Kg is 3g / 10min, and the notched impact strength is 15kJ / m 2 , specific gravity is 0.95g / cm 3 ;

[0045] PP washing machine recycled material is PP washing machine recycled crushed material, the melt index at 230℃, 2.16Kg is 30g / 10min, and the notched impact strength is 6kJ / m 2 , specific gravity is 0.96g / cm 3 ;

[0046] PP multi-color cup recycled material is PP flower cup recycled crushed material, the melt index at 230℃ and 2.16Kg is 15g / 10min, and the notched impact strength is 5kJ / m 2 , specific gravity is 0.93g / cm 3 ;

[0047] Flame retardant PP recycled material is flame retardant PP recycled crushed material, the melt index at 230℃ and 2.16Kg is 3kJ / m 2 , notched impact strength is 6kJ / m 2 , specific gravity is 1.02g / cm 3 .

[0048] Example 1

[0049] 2 g of ammonium polyphosphate, 1 g of 2,3-dimethyl-2,3-diphenylbutane and 7 g of flame-retardant PP recycled material were mixed evenly to obtain a composite flame retardant.

[0050] Example 2

[0051] 1 g of ammonium polyphosphate, 0.5 g of 2,3-dimethyl-2,3-diphenylbutane and 6 g of flame-retardant PP recycled material were uniformly mixed to obtain a composite flame retardant.

[0052] Example 3

[0053] 3 g of ammonium polyphosphate, 1.5 g of 2, 3-dimethyl-2, 3-diphenylbutane and 8 g of flame-retardant PP recycled material were uniformly mixed to obtain a composite flame retardant.

[0054] Comparative Example 1

[0055] The difference from Example 1 is that 2,3-dimethyl-2,3-diphenylbutane is replaced with ammonium polyphosphate of the same mass, and the rest are the same.

[0056] Comparative Example 2

[0057] The difference from Example 1 is that ammonium polyphosphate is replaced by pentaerythritol phosphate melamine of the same mass, and the rest are the same.

[0058] Comparative Example 3

[0059] The difference from Example 1 is that the melt index of the flame retardant PP recycled material at 230°C and 2.16 kg is 10 kJ / m 2 , notched impact strength is 12kJ / m 2 , specific gravity is 0.95g / cm 3 , the rest are the same.

[0060] Application Example 1-5, Comparative Application Example 1-3

[0061] The specific formula composition of flame retardant recycled PP, by weight, is shown in Table 1:

[0062] Table 1

[0063]

[0064]

[0065] Application Example 1-5 and Comparative Application Example 1-3 The preparation method of flame-retardant recycled PP is as follows: PP mixed color acrylic recycled material, PP paint barrel recycled material, PP washing machine recycled material, PP multi-color cup recycled material, composite flame retardant and polyethylene wax are mixed in a melt extruder for primary granulation to obtain primary granules; the primary granules, 2,6-tert-butyl-4-methylphenol, bis(3,5-tert-butyl-4-hydroxyphenyl) sulfide and color powder are mixed in a melt extruder for secondary granulation to obtain flame-retardant recycled PP;

[0066] The temperatures of each zone of the melt extruder are: zone 1 temperature is 195°C, zone 2 temperature is 200°C, zone 3 temperature is 230°C, zone 4 temperature is 230°C, zone 5 temperature is 200°C, zone 6 temperature is 190°C, and the screw speed is 36r / min.

[0067] Comparative Application Example 4

[0068] The difference from Application Example 2 is that the melt index of the PP paint barrel recycled material at 230°C and 2.16Kg is 6g / 10min and the notched impact strength is 22kJ / m 2 , specific gravity is 0.96g / cm 3 , the rest are the same.

[0069] Comparative Application Example 5

[0070] The difference from Application Example 2 is that the PP mixed color acrylic recycled material is replaced with PP multi-color cup recycled material of the same quality, and the rest are the same.

[0071] Comparative Application Example 6

[0072] The difference from Application Example 2 is that the PP washing machine recycled material is replaced with the PP toilet cover recycled material of the same quality. The PP toilet cover recycled material is the PP toilet cover recycled crushed material, and the melt index at 230°C and 2.16Kg is 18g / 10min, and the notched impact strength is 8kJ / m 2 , specific gravity is 0.93g / cm 3 , the rest are the same.

[0073] Comparative Application Example 7

[0074] The difference from Application Example 2 is that the content of the formula components is different. The specific formula composition is shown in Table 2 by weight:

[0075] Table 2

[0076]

[0077] Comparative Application Example 8

[0078] The difference from Application Example 2 is that the preparation method of flame retardant recycled PP is: PP mixed color propylene recycled material, PP paint barrel recycled material, PP washing machine recycled material, PP multi-color cup recycled material, composite flame retardant, polyethylene wax, 2,6-tert-butyl-4-methylphenol, bis(3,5-tert-butyl-4-hydroxyphenyl) sulfide and color powder are mixed in a melt extruder for granulation to obtain flame retardant recycled PP; the rest are the same.

[0079] Comparative Application Example 9

[0080] The difference from Application Example 2 is that the preparation method of flame retardant recycled PP is: PP mixed color propylene recycled material, PP paint barrel recycled material, PP washing machine recycled material, PP multi-color cup recycled material and polyethylene wax are mixed in a melt extruder for primary granulation to obtain primary granules; the primary granules, composite flame retardant, 2,6-tert-butyl-4-methylphenol, bis(3,5-tert-butyl-4-hydroxyphenyl) sulfide and color powder are mixed in a melt extruder for secondary granulation to obtain flame retardant recycled PP; the rest are the same.

[0081] Comparative Application Example 10

[0082] The difference from Application Example 2 is that the temperatures of each zone of the melt extruder are: zone 1 temperature is 170°C, zone 2 temperature is 180°C, zone 3 temperature is 210°C, zone 4 temperature is 210°C, zone 5 temperature is 190°C, and zone 6 temperature is 180°C; the rest are the same.

[0083] Comparative Application Example 11

[0084] The difference from Application Example 2 is that the temperatures of each zone of the melt extruder are: zone 1 temperature is 230°C, zone 2 temperature is 230°C, zone 3 temperature is 230°C, zone 4 temperature is 230°C, zone 5 temperature is 230°C, zone 6 temperature is 230°C; the rest are the same.

[0085] Test example: The flame retardant recycled PP of all application examples and comparative application examples were tested as follows:

[0086] 1. Melt index: tested in accordance with GB / T 3682.12018;

[0087] 2. Specific gravity: Tested in accordance with GB / T 1033.1-2008 liquid specific gravity bottle method;

[0088] 3. Elongation at break: Tested in accordance with GB / T 1040.1-2018;

[0089] 4. Notched impact strength: tested in accordance with GB / T 1843-2008;

[0090] 5. Flame retardant properties: The test was conducted in accordance with the vertical combustion test of GB / T 2408-2008; the results are shown in Table 3 and Table 4.

[0091] Table 3

[0092]

[0093] Table 4

[0094]

[0095] It can be seen from Table 3 and Table 4 that:

[0096] The flame-retardant recycled PP of application examples 1-5 has a large melt index, a small specific gravity, a high elongation at break, a high notched impact strength, and a flame retardant performance reaching V0 level;

[0097] Comparative Application Example 1-3 Due to the change in the composition of the composite flame retardant, the flame retardant properties of the flame retardant recycled PP obtained in Comparative Application Example 1-2 deteriorate, and the elongation at break of the flame retardant recycled PP obtained in Comparative Application Example 3 decreases.

[0098] Comparative Application Examples 4-6 Due to the change in the composition of the recycled materials in the formula, the elongation at break and the notched impact strength of the flame-retardant recycled PP obtained decreased to varying degrees, and the melt index of Comparative Example 6 also decreased.

[0099] In comparative application example 7, since the formula content is not within the preferred range, the elongation at break and notched impact strength of the flame-retardant recycled PP obtained are reduced.

[0100] Due to the change in the preparation method of flame-retardant recycled PP in comparative application examples 8-11, the flame retardant properties of the obtained flame-retardant recycled PP deteriorate; the elongation at break and the notched impact strength decrease to varying degrees, and the melt index of comparative example 10 also decreases.

[0101] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A composite flame retardant, characterized in that: The raw materials include: ammonium polyphosphate, 2, 3-dimethyl-2, 3-diphenylbutane and flame-retardant PP recycled materials; the mass ratio of the ammonium polyphosphate, 2, 3-dimethyl-2, 3-diphenylbutane and flame-retardant PP recycled materials is 1-3:0.5-1.5:6-8.

2. The composite flame retardant according to claim 1, characterized in that: The flame retardant PP recycled material has a melt index of 2-4 g / 10 min at 230° C. and 2.16 kg, and a notched impact strength of 4-8 kJ / m 2 , specific gravity is 0.99-1.05g / cm 3 .

3. The method for preparing the composite flame retardant according to any one of claims 1 to 2, characterized in that: The method comprises the following steps: uniformly mixing ammonium polyphosphate, 2,3-dimethyl-2,3-diphenylbutane and flame-retardant PP recycled material to obtain a composite flame retardant.

4. Use of the composite flame retardant according to any one of claims 1 to 2 in the preparation of flame retardant recycled plastics.

5. A flame retardant recycled PP, characterized in that: Calculated by mass, the raw materials include: 50-70 parts of PP mixed color acrylic recycled materials, 5-15 parts of PP paint bucket recycled materials, 5-15 parts of PP washing machine recycled materials, 10-30 parts of PP multi-color cup recycled materials, 1-5 parts of the composite flame retardant according to any one of claims 1-2, 0.2-1 parts of antioxidants, 0.5-1 parts of lubricants, and 0.01-0.25 parts of color powder.

6. The flame retardant recycled PP according to claim 5, characterized in that: The PP heterochromatic recycled material has a melt index of 10-20 g / 10 min at 230° C. and 2.16 kg, and a notched impact strength of 4-5 kJ / m 2 , specific gravity is 0.93-0.95g / cm 3 The melt index of the PP paint barrel recycled material at 230°C and 2.16Kg is 3-5g / 10min, and the notched impact strength is 10-20kJ / m 2 , specific gravity is 0.93-0.95g / cm 3 The PP washing machine recycled material has a melt index of 25-35g / 10min at 230°C and 2.16Kg, and a notched impact strength of 4-6kJ / m 2 , specific gravity is 0.93-0.96g / cm 3 The PP multi-color cup recycled material has a melt index of 10-20g / 10min and a notched impact strength of 4-6kJ / m at 230°C and 2.16Kg. 2 , specific gravity is 0.93-0.95g / cm 3 .

7. The flame retardant recycled PP according to claim 6, characterized in that: The antioxidant is a mixture of 2,6-tert-butyl-4-methylphenol and bis(3,5-tert-butyl-4-hydroxyphenyl)sulfide, and the mass ratio of the two is 0.1-0.5:0.1-0.

5.

8. The method for preparing the flame retardant recycled PP according to any one of claims 5 to 7 comprises the following steps: PP mixed color acrylic recycled materials, PP paint barrel recycled materials, PP washing machine recycled materials, PP multi-color cup recycled materials, composite flame retardant and lubricant are mixed and granulated once to obtain primary granules; the primary granules, antioxidant and color powder are mixed and granulated twice to obtain flame retardant recycled PP.

9. The preparation method according to claim 8, characterized in that: The primary granulation and the secondary granulation are both carried out in a melt extruder; the temperature of each zone of the melt extruder is: the temperature of zone 1 is 190-200°C, the temperature of zone 2 is 195-205°C, the temperature of zone 3 is 220-240°C, the temperature of zone 4 is 220-240°C, the temperature of zone 5 is 190-210°C, and the temperature of zone 6 is 180-200°C.

10. The preparation method according to claim 9, wherein the temperatures of the zones of the melt extruder are: zone 1 is 195°C, zone 2 is 200°C, zone 3 is 230°C, zone 4 is 230°C, zone 5 is 200°C, and zone 6 is 190°C.

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