Rotational molding polyethylene with high oxygen index and preparation method thereof

Abstract

The invention discloses high-oxygen-index rotational molding polyethylene and a preparation method thereof, and relates to the field of flame-retardant materials. The polyethylene with the high oxygen index comprises the following components in percentage by weight: 47.72%-64.82% of polyethylene, 3.74%-44.56% of chlorinated paraffin-70, 8.91%-44.56% of bromotriazine and 5.01%-7.72% of antimony trioxide. The chlorine-bromine-antimony efficient flame-retardant system and the linear low-density polyethylene are compounded to prepare the flame-retardant polyethylene, compared with a traditional bromine-antimony flame-retardant system, the chlorine-bromine-antimony flame-retardant system added with the same proportion of flame retardant can obtain a composite polyethylene material with the oxygen index larger than 40%, and the flame-retardant effect is good; the box body product processed through the rotational molding technology has good flame retardant capacity, the preparation method is simple, complex equipment is not needed, and industrial operation is easy to achieve.

Description

Technical Field

[0001] The invention belongs to the field of flame retardant materials, and in particular relates to high oxygen index rotomolded polyethylene and a preparation method thereof. Background Art

[0002] Polyethylene is widely used in storage, chemical industry, packaging, transportation, construction materials, electronics and electrical engineering due to its non-toxic and odorless, low price and excellent performance. However, polyethylene has a low oxygen index and is a flammable material, which is easy to cause fire and poses a huge threat to people's lives and property safety. Therefore, strengthening the research on the flame retardancy of polyethylene has always been a hot research direction.

[0003] At present, flame retardant additives can be divided into organic flame retardant additives and inorganic flame retardant additives. Organic flame retardant systems include bromine and nitrogen flame retardants, and inorganic flame retardant systems include antimony trioxide and silicon flame retardant systems. However, the oxygen index of linear low-density polyethylene added with flame retardant additives on the market is less than 40%. For example, CN1927929A discloses a linear low-density polyethylene added composite flame retardant material, in which palygorskite powder, halogen-free flame retardant, and linear low-density polyethylene are used to prepare flame-retardant polyethylene. The oxygen index of the composite polyethylene material obtained is only up to 30%. CN104877212A discloses a HDPE flame retardant material for mining and a preparation method thereof, wherein HDPE, zinc oxide, decabromodiphenyl ether, calcium stearate, magnesium hydroxide, 2,6-di-tert-butyl-p-cresol, antioxidant, EVA, lead stearate, EVOH, flame retardant, CPE, UHMWPE, EPDM and organic montmorillonite are used to prepare flame retardant polyethylene, and the oxygen index of the obtained composite polyethylene material is only up to 34%. Summary of the invention

[0004] One purpose of the present invention is to provide a high oxygen index rotomolded polyethylene, which is prepared by compounding linear low-density polyethylene and a chlorine-bromine-antimony high-efficiency flame retardant system. The oxygen index of the obtained composite polyethylene material is greater than 40%, and the flame retardant effect is good. Another purpose is to provide a preparation method of high oxygen index rotomolded polyethylene, which is simple, does not require complex equipment, and is easy to realize industrial operation.

[0005] To achieve the above object, the present invention provides the following technical solutions: A high oxygen index rotomolding polyethylene comprises the following components: 47.72-64.82% polyethylene, 3.74-44.56% chlorinated paraffin-70, 8.91-44.56% bromotriazine and 5.01-7.72% antimony trioxide.

[0006] Preferably, the high oxygen index rotomolded polyethylene comprises the following components: 47.73% polyethylene, 5.57% chlorinated paraffin-70, 38.98% bromotriazine, and 7.72% antimony trioxide.

[0007] The polyethylene is low-density polyethylene with a density of 0.934 g / cm 3 At 190°C and 2.16kg, the melt mass flow rate is 5.0-20.0g / 10min. This performance polyethylene material ensures that the auxiliary materials in the material can be fully dispersed at high temperatures.

[0008] Preferably, the polyethylene has a melt mass flow rate of 7.0 g / 10 min at 190° C. and 2.16 kg.

[0009] The antimony trioxide is a white powder with a bulk density of 0.700-0.800 g / cm3 and is used as an auxiliary flame retardant.

[0010] The bromotriazine is a white powder with a bulk density of 0.500-0.600 g / cm3. It is used as a main flame retardant and does not produce toxic substances during combustion.

[0011] The chlorinated paraffin-70 is a white powder with a bulk density of 0.400-0.500 g / cm3. It is used as an auxiliary flame retardant and has the characteristic of low smoke.

[0012] The present invention also provides another technical solution: A method for preparing high oxygen index rotomolded polyethylene comprises the following steps: S1: linear low-density polyethylene, bromotriazine, antimony trioxide and chlorinated paraffin-70 are placed in a blender and mixed; S2: melt blending with a twin-screw extruder, extruding into granules, and then putting the granules into a twin-screw extruder for melt blending; S3: Grinding the polyethylene composite particles obtained in the above steps on a grinding disc using a plastic grinder to obtain polyethylene flame-retardant rotational molding material.

[0013] The mixing time of each component in S1 is 10-20 minutes.

[0014] During the melt blending in S2, the melt temperature is 185-200° C. and the screw speed is 280-300 rpm.

[0015] In the S3, the grinding disc temperature is 70-75°C, and the grinding disc rotation speed is 2800-3000rpm.

[0016] Preferably, the bulk density of the polyethylene composite powder prepared by the present invention is 0.300-0.500 g / cm 3, powder fluidity ≤30s / 100g, melt flow rate is 2.0-10.0g / 10min at 90℃, 2.16kg, particle size distribution D95≤500μm, D20≥150μm.

[0017] When the material is ignited by flame, chlorinated paraffin-70 and brominated triazine in the flame retardant system will simultaneously generate antimony trichloride, antimony tribromide, antimony oxychloride and antimony oxybromide. Due to the different bond energies required to generate chlorine-oxygen bonds and bromine-oxygen bonds, the temperature of the same cross section of the material is uneven, which helps to improve the oxygen index of the material. In addition, the chlorine free radicals and bromine free radicals released by antimony trichloride and antimony tribromide combine with the hydrogen free radicals generated by the combustion of polyethylene materials at different speeds, which can further quench the flame for a longer period of time. In addition, due to the different densities of antimony trichloride and antimony tribromide, when the material is ignited by flame, they can fully cover the surface of the material, making it better to block the contact between the surface of the material and the oxygen in the air, thereby achieving the desired oxygen concentration and improving the oxygen index.

[0018] Therefore, the present invention has the following beneficial effects: (1) The chlorine-bromine-antimony high-efficiency flame retardant system is compounded with linear low-density polyethylene to prepare flame-retardant polyethylene. The oxygen index of the obtained composite polyethylene material is greater than 40%, and the flame retardant effect is good; the box products processed by the rotational molding process have good flame retardant ability. Compared with the traditional bromine-antimony flame retardant system, the chlorine-bromine-antimony flame retardant system with the same proportion of flame retardant can obtain a polyethylene material with a higher oxygen index; (2) The rotomolded polyethylene material of the present invention has a simple preparation method, does not require complicated equipment, and is easy to implement industrial operation. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described below through specific embodiments.

[0020] In the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or commonly used in the art. The linear low-density polyethylene, antimony trioxide, bromotriazine and chlorinated paraffin-70 of the present invention are all products sold on the market. Among them, antimony trioxide was purchased from Yunnan Muli Company, bromotriazine was purchased from Shandong Weidong Chemical Co., Ltd., and chlorinated paraffin-70 was purchased from Zibo Shengke Flame Retardant Material Co., Ltd.

[0021] The linear low-density polyethylene composite powder of the present invention meets the requirements of bulk density of 0.300-0.500 g / cm3, powder fluidity ≤30 s / 100 g, melt flow rate (tested at 190°C 2.16 kg) of 2.0-10.0 g / 10 min, particle size distribution D95 ≤500 μm, and D20 ≥150 μm.

[0022] Example 1 A high oxygen index rotomolding polyethylene: linear low-density polyethylene (density 0.934 g / cm3, melt flow rate [190°C 2.16 kg] is 7.0 g / 10 min), bromotriazine, antimony trioxide and chlorinated paraffin-70 are taken. The total mass parts are 100 parts, and the mass ratio of each raw material component is polyethylene: chlorinated paraffin-70: bromotriazine: antimony trioxide = 47.74:4.05:40.49:7.72.

[0023] A preparation method of high oxygen index rotomolded polyethylene comprises the following steps: adding polyethylene, chlorinated paraffin-70, bromotriazine and antimony trioxide into a mixer for 10 minutes, melt-blending the mixed materials with a twin-screw extruder, extruding and granulating, then putting the mixed materials into the twin-screw extruder for melt-blending again, and extruding again, wherein the extrusion process parameters are as follows: the melt temperature is 200 DEG C and the screw speed is 300 rpm; and finally grinding the granulated particles with a plastic grinding machine, wherein the grinding process parameters are as follows: the grinding disc temperature is 70 DEG C and the grinding disc speed is 2900 rpm.

[0024] Example 2 A high oxygen index rotomolding polyethylene: linear low-density polyethylene (density 0.934 g / cm3, melt flow rate [190°C 2.16 kg] is 7.0 g / 10 min), bromotriazine, antimony trioxide and chlorinated paraffin-70 are taken. The total mass parts are 100 parts, and the mass ratio of each raw material component is polyethylene: chlorinated paraffin-70: bromotriazine: antimony trioxide = 47.74:4.95:39.59:7.72.

[0025] A preparation method of high oxygen index rotomolded polyethylene comprises the following steps: adding polyethylene, chlorinated paraffin-70, bromotriazine and antimony trioxide into a mixer for 15 minutes, melt-blending the mixed materials with a twin-screw extruder, extruding and granulating, then putting the mixed materials into the twin-screw extruder for melt-blending again, and extruding again, wherein the extrusion process parameters are as follows: the melt temperature is 195°C and the screw speed is 300rpm; and finally grinding the granulated particles with a plastic grinding machine, wherein the grinding process parameters are as follows: the grinding disc temperature is 70°C and the grinding disc speed is 2800rpm.

[0026] Example 3 A high oxygen index rotomolding polyethylene: linear low-density polyethylene (density 0.934 g / cm3, melt flow rate [190°C 2.16 kg] is 7.0 g / 10 min), bromotriazine, antimony trioxide and chlorinated paraffin-70 are taken. The total mass parts are 100 parts, and the mass ratio of each raw material component is polyethylene: chlorinated paraffin-70: bromotriazine: antimony trioxide = 47.73:5.57:38.98:7.72.

[0027] A preparation method of high oxygen index rotomolded polyethylene comprises the following steps: adding polyethylene, chlorinated paraffin-70, bromotriazine and antimony trioxide into a mixer for 10 minutes, melt-blending the mixed materials with a twin-screw extruder, extruding and granulating, then putting the mixed materials into the twin-screw extruder for melt-blending again, and extruding again, wherein the extrusion process parameters are as follows: the melt temperature is 200 DEG C and the screw speed is 300 rpm; and finally grinding the granulated particles with a plastic grinding machine, wherein the grinding process parameters are as follows: the grinding disc temperature is 70 DEG C and the grinding disc speed is 2900 rpm.

[0028] Example 4 A high oxygen index rotomolding polyethylene: linear low-density polyethylene (density 0.934 g / cm3, melt flow rate [190°C 2.16 kg] is 7.0 g / 10 min), bromotriazine, antimony trioxide and chlorinated paraffin-70 are taken. The total mass parts are 100 parts, and the mass ratio of each raw material component is polyethylene: chlorinated paraffin-70: bromotriazine: antimony trioxide = 47.76:6.36:38.16:7.72.

[0029] A preparation method of high oxygen index rotomolded polyethylene comprises the following steps: adding polyethylene, chlorinated paraffin-70, bromotriazine and antimony trioxide into a mixer for 10 minutes, melt-blending the mixed materials with a twin-screw extruder, extruding and granulating, then putting the mixed materials into the twin-screw extruder for melt-blending again, and extruding again, wherein the extrusion process parameters are as follows: the melt temperature is 200 DEG C and the screw speed is 300 rpm; and finally grinding the granulated particles with a plastic grinding machine, wherein the grinding process parameters are as follows: the grinding disc temperature is 75 DEG C and the grinding disc speed is 2900 rpm.

[0030] Example 5 A high oxygen index rotomolding polyethylene: linear low-density polyethylene (density 0.934 g / cm3, melt flow rate [190°C 2.16 kg] is 7.0 g / 10 min), bromotriazine, antimony trioxide and chlorinated paraffin-70 are taken. The total mass parts are 100 parts, and the mass ratio of each raw material component is polyethylene: chlorinated paraffin-70: bromotriazine: antimony trioxide = 47.72:35.65:8.91:7.72.

[0031] A preparation method of high oxygen index rotomolded polyethylene comprises the following steps: adding polyethylene, chlorinated paraffin-70, bromotriazine and antimony trioxide into a mixer for 10 minutes, melt-blending the mixed materials with a twin-screw extruder, extruding and granulating, then putting the mixed materials into the twin-screw extruder for melt-blending again, and extruding again, wherein the extrusion process parameters are as follows: the melt temperature is 200 DEG C and the screw speed is 300 rpm; and finally grinding the granulated particles with a plastic grinding machine, wherein the grinding process parameters are as follows: the grinding disc temperature is 70 DEG C and the grinding disc speed is 2900 rpm.

[0032] Example 6 A high oxygen index rotomolding polyethylene: linear low-density polyethylene (density 0.934 g / cm3, melt flow rate [190°C 2.16 kg] is 7.0 g / 10 min), bromotriazine, antimony trioxide and chlorinated paraffin-70 are taken. The total mass parts are 100 parts, and the mass ratio of each raw material component is polyethylene: chlorinated paraffin-70: bromotriazine: antimony trioxide = 62.03:3.80:26.62:7.55.

[0033] A preparation method of high oxygen index rotomolded polyethylene comprises the following steps: adding polyethylene, chlorinated paraffin-70, bromotriazine and antimony trioxide into a mixer for 15 minutes, melt-blending the mixed materials with a twin-screw extruder, extruding and granulating, then putting the mixed materials into the twin-screw extruder for melt-blending again, and extruding again, wherein the extrusion process parameters are as follows: the melt temperature is 200 DEG C and the screw speed is 300 rpm; and finally grinding the granulated particles with a plastic grinding machine, wherein the grinding process parameters are as follows: the grinding disc temperature is 70 DEG C and the grinding disc speed is 3000 rpm.

[0034] Example 7 A high oxygen index rotomolding polyethylene: linear low-density polyethylene (density 0.934 g / cm3, melt flow rate [190°C 2.16 kg] is 7.0 g / 10 min), bromotriazine, antimony trioxide and chlorinated paraffin-70 are taken. The total mass parts are 100 parts, and the mass ratio of each raw material component is polyethylene: chlorinated paraffin-70: bromotriazine: antimony trioxide = 63.03:3.86:27.04:6.07.

[0035] A preparation method of high oxygen index rotomolded polyethylene comprises the following steps: adding polyethylene, chlorinated paraffin-70, bromotriazine and antimony trioxide into a mixer for 10 minutes, melt-blending the mixed materials with a twin-screw extruder, extruding and granulating, then putting the mixed materials into the twin-screw extruder for melt-blending again, and extruding again, wherein the extrusion process parameters are as follows: the melt temperature is 195 DEG C and the screw speed is 340 rpm; and finally grinding the granulated particles with a plastic grinding machine, wherein the grinding process parameters are as follows: the grinding disc temperature is 70 DEG C and the grinding disc speed is 2800 rpm.

[0036] Example 8 A high oxygen index rotomolding polyethylene: linear low-density polyethylene (density 0.934 g / cm3, melt flow rate [190°C 2.16 kg] is 7.0 g / 10 min), bromotriazine, antimony trioxide and chlorinated paraffin-70 are taken. The total mass parts are 100 parts, and the mass ratio of each raw material component is polyethylene: chlorinated paraffin-70: bromotriazine: antimony trioxide = 64.82:3.74:26.43:5.01.

[0037] A preparation method of high oxygen index rotomolded polyethylene comprises the following steps: adding polyethylene, chlorinated paraffin-70, bromotriazine and antimony trioxide into a mixer for 15 minutes, melt-blending the mixed materials with a twin-screw extruder, extruding and granulating, then putting the mixed materials into the twin-screw extruder for melt-blending again, and extruding again, wherein the extrusion process parameters are as follows: the melt temperature is 200 DEG C and the screw speed is 300 rpm; and finally grinding the granulated particles with a plastic grinding machine, wherein the grinding process parameters are as follows: the grinding disc temperature is 70 DEG C and the grinding disc speed is 2800 rpm.

[0038] Comparative Example 1 A rotomolding polyethylene: polyethylene (density 0.934 g / cm3, melt flow rate [190℃2.16Kg] is 7.0 g / 10min), bromotriazine, and antimony trioxide are taken. The total mass parts are 100 parts, and the mass ratio of each raw material component is polyethylene: bromotriazine: antimony trioxide = 47.72:44.56:7.72.

[0039] A preparation method of rotomolded polyethylene comprises the following steps: adding polyethylene, bromotriazine and antimony trioxide into a mixer for 20 minutes, melt-blending the mixed materials with a twin-screw extruder, extruding and granulating, then putting the mixed materials into the twin-screw extruder for melt-blending again, and extruding again, wherein the extrusion process parameters are as follows: the melt temperature is 185°C and the screw speed is 340rpm; and finally grinding the granulated particles with a plastic grinding machine, wherein the grinding process parameters are as follows: the grinding disc temperature is 70°C and the grinding disc speed is 3900rpm.

[0040] The difference between this comparative example and Example 1 is that chlorinated paraffin-70 is not added, and an equal proportion of bromotriazine is used instead.

[0041] Comparative Example 2 A rotomolding polyethylene: polyethylene (density 0.934 g / cm3, melt flow rate [190℃2.16Kg] is 7.0 g / 10min), chlorinated paraffin-70, and antimony trioxide are taken. The total mass parts are 100 parts, and the mass ratio of each raw material component is polyethylene: chlorinated paraffin-70: antimony trioxide = 47.72:44.56:7.72.

[0042] A method for preparing rotomolded polyethylene comprises the following steps: adding polyethylene, chlorinated paraffin-70 and antimony trioxide into a mixer for 15 minutes, melt-blending the mixed materials with a twin-screw extruder, extruding and granulating, then putting the mixed materials into the twin-screw extruder for melt-blending again, and extruding again, wherein the extrusion process parameters are as follows: the melt temperature is 195°C and the screw speed is 300rpm; and finally grinding the granulated particles with a plastic grinding machine, wherein the grinding process parameters are as follows: the grinding disc temperature is 70°C and the grinding disc speed is 2800rpm.

[0043] The difference between this comparative example and Example 1 is that no brominated triazine is added, and an equal proportion of chlorinated paraffin-70 is used instead.

[0044] Table 1 Components in Examples and Comparative Examples. Polyethylene Chlorinated paraffin-70 Bromotriazine Antimony trioxide Example 1 44.74 4.05 40.49 7.72 Example 2 44.74 4.95 39.59 7.72 Example 3 44.73 5.57 38.98 7.72 Example 4 47.76 6.36 38.16 7.72 Example 5 47.72 35.65 8.91 7.72 Example 6 62.03 3.80 26.62 7.55 Example 7 63.30 3.86 27.04 6.07 Example 8 64.82 3.74 26.43 5.01 Comparative Example 1 44.72 -- 44.56 7.72 Comparative Example 2 44.72 44.56 -- 7.72

[0045] Performance Testing 1. Oxygen index determination Test method: The oxygen index of the material is tested by the oxygen index method (LOI). The experiment is carried out by using the ASTM D2863 standard. The material is cut into standard sizes (about 150mm×10mm×5mm), placed in a vertical combustion device, the ratio of oxygen and nitrogen is adjusted, the sample is ignited, and the relationship between the oxygen concentration and the extinguishing of the sample is recorded to obtain the oxygen index of the material. The test instrument uses an oxygen index tester.

[0046] A high oxygen index indicates that the material is not easy to burn, and a low oxygen index indicates that the material is easy to burn. It is generally believed that an oxygen index of less than 22% is a flammable material, an oxygen index between 22 and 27% is a combustible material, and an oxygen index of more than 27% is a flame retardant material.

[0047] The performance test results of chlorine-bromine-antimony flame retardant system high oxygen index rotational molded polyethylene composite materials are shown in Table 2.

[0048] Table 2 Performance test results of high oxygen index rotomolded polyethylene composite materials.

[0049] It can be seen from Table 2 that in the above test, the oxygen index of the polyethylene materials of Comparative Examples 1-2 is lower than 40%. Comparative Examples 1 and 2 use chlorinated paraffin-70 and antimony trioxide alone or bromotriazine and antimony trioxide alone as flame retardants. Therefore, it can be seen that when chlorinated paraffin-70 and antimony trioxide or bromotriazine and antimony trioxide are used alone, the oxygen index that can be improved is limited, and the prepared polyethylene material has poor flame retardant effect. The reason for this is that in the flame retardant process of Comparative Examples 1 and 2, only bromine or chlorine captures hydroxyl radicals, oxygen radicals and hydrogen radicals respectively during the combustion process to generate combustion inert substances; while in Examples 1-8 of the present invention, a chlorine-bromine-antimony high-efficiency flame retardant system composed of chlorinated paraffin-70, bromotriazine and antimony trioxide is used. When the material is ignited by the flame, the chlorinated paraffin-70 and bromotriazine in the flame retardant system will simultaneously generate antimony trichloride, antimony tribromide, antimony oxychloride and antimony oxybromide. Due to the different bond energies required to generate chlorine oxygen bonds and bromine oxygen bonds, the temperature of the same cross section of the material is uneven, which helps to improve the oxygen index of the material. In addition, the chlorine radicals and bromine radicals released by antimony trichloride and antimony tribromide combine with the hydrogen radicals generated by the combustion of polyethylene materials at different speeds, which can also further quench the flame for a long time. In addition, due to the different densities of antimony trichloride and antimony tribromide, when the material is ignited by the flame, it can fully cover the surface of the material, so that it can better block the contact between the surface of the material and the oxygen in the air, thereby achieving the desired oxygen concentration and improving the oxygen index.

[0050] 2. Vertical combustion test Test method: The polyethylene materials prepared in Examples 1-8 and Comparative Examples 1-2 were made into 3.2×13×100 mm3 strips with flame retardant polymer core materials, and vertical combustion tests were performed according to standard ISO-9773. The results were graded, and the grade categories were VTM-0, VTM-1, VTM-2, and not applicable, indicating that the flammability of the materials gradually increased. The test results are shown in Table 3.

[0051] Table 3 Vertical burning test results.

[0052] As can be seen from Table 3, the vertical combustion grade of Examples 1-8 is VTM-0, which has a good flame retardant effect, while the vertical combustion grades of Comparative Examples 1-2, which use only the chlorine-antimony flame retardant system of chlorinated paraffin-70 and antimony trioxide, or the bromine-antimony flame retardant system of bromotriazine and antimony trioxide, are VTM-1 and VTM-2, respectively, and the flame retardant effect is poor. This shows that the polyethylene material prepared by the present invention using the chlorine-bromine-antimony high-efficiency flame retardant system composed of chlorinated paraffin-70, bromotriazine and antimony trioxide has a good flame retardant effect.

[0053] The above data prove that the chlorine-bromine-antimony flame retardant system with the same proportion of flame retardants can obtain a polyethylene material with a higher oxygen index than the bromine-antimony flame retardant system and the chlorine-antimony flame retardant system. Therefore, the invention uses the chlorine-bromine-antimony high-efficiency flame retardant system to prepare a linear low-density polyethylene rotomolding material with an oxygen index of 46.3%, good flame retardant effect, and a simple preparation method. The material can be molded using ordinary injection molding and rotational molding methods, which helps to improve production efficiency.

[0054] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A high oxygen index rotomolded polyethylene, characterized in that: The invention comprises the following components: 47.72-64.82% of polyethylene, 3.74-44.56% of chlorinated paraffin, 8.91-44.56% of bromotriazine and 5.01-7.72% of antimony trioxide.

2. The high oxygen index rotomolded polyethylene according to claim 1, characterized in that: The invention comprises the following components: 47.73% polyethylene, 5.57% chlorinated paraffin-70, 38.98% bromotriazine and 7.72% antimony trioxide.

3. The high oxygen index rotomolded polyethylene according to claim 1 or 2, characterized in that: The polyethylene is low-density polyethylene, and the melt mass flow rate is 5.0-20.0 g / 10 min at 190° C. and 2.16 kg.

4. The high oxygen index rotomolded polyethylene according to claim 1, characterized in that: The bulk density of the antimony trioxide is 0.700-0.800 g / cm 3 .

5. The high oxygen index rotomolded polyethylene according to claim 1, characterized in that: The bulk density of the bromotriazine is 0.500-0.600 g / cm 3 .

6. The high oxygen index rotomolded polyethylene according to claim 1, characterized in that: The bulk density of the chlorinated paraffin-70 is 0.400-0.500 g / cm 3 .

7. A method for preparing high oxygen index rotomolded polyethylene, characterized in that: The following steps are involved: S1: linear low-density polyethylene, bromotriazine, antimony trioxide and chlorinated paraffin-70 are placed in a blender and mixed; S2: melt blending with a twin-screw extruder, extruding into granules, and then putting the granules into a twin-screw extruder for melt blending; S3: Grinding the polyethylene composite particles obtained in the above steps on a grinding disc using a plastic grinder to obtain polyethylene flame-retardant rotational molding material.

8. The method for preparing high oxygen index rotomolded polyethylene according to claim 7, characterized in that: The mixing time of each component in S1 is 10-20 minutes.

9. The method for preparing high oxygen index rotomolded polyethylene according to claim 7, characterized in that: During the melt blending in S2, the melt temperature is 185-200° C. and the screw speed is 280-300 rpm.

10. The method for preparing high oxygen index rotomolded polyethylene according to claim 7, characterized in that: In the S3, the grinding disc temperature is 70-75°C, and the grinding disc rotation speed is 2800-3000rpm.

Images