Special high-density crosslinked polyethylene rotational molding material and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses a high-density crosslinked polyethylene rotational molding special material and a preparation method thereof.The high-density crosslinked polyethylene rotational molding special material is prepared from 85%-95% of high-density polyethylene, 5%-15% of low-density polyethylene, 0.1%-0.5% of a crosslinking agent and 0.2%-2% of a crosslinking accelerant. The low-activity cross-linking agent and the high-activity cross-linking agent are compounded, so that partial cross-linking targeting of the low-activity cross-linking agent occurs on a long chain of the low-density polyethylene, the toughness of the polyethylene is further improved, and the toughness of the rotational molding cross-linked polyethylene is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, in particular to a high-density cross-linked polyethylene special rotational molding material and a preparation method thereof. Background Art

[0002] Polyethylene is an important polymer material and is widely used in industry, agriculture and daily life. Polyethylene has poor high temperature resistance, and its mechanical properties and chemical resistance sometimes cannot meet the actual use needs. Because the modification of polyethylene has always been the key to the development and application of polyethylene products, polyethylene cross-linking technology is an important polyethylene modification technology; the high temperature resistance, mechanical properties, environmental stress cracking resistance, chemical corrosion resistance, creep resistance and other properties of cross-linked modified polyethylene can be greatly improved.

[0003] Roto-molding is a hollow molding method for thermoplastic materials. This method is to add plastic powder into the mold, knead it, and then rotate the mold continuously along two vertical axes to heat it, gradually and evenly coat it, melt it and adhere it to the entire surface of the mold cavity, and mold it into the required shape. It is then cooled and shaped into a product. The roto-molding process is suitable for hollow plastic products with large volume and complex structure, and is widely used in engineering machinery, automobiles, medical and military industries, home appliances, amusement and other fields.

[0004] At present, there are many technical problems in applying cross-linked polyethylene to the rotational molding process. For example, a cross-linked polyethylene composition with improved processing performance disclosed in publication number CN104334630B, in which a free radical inhibitor is added to increase the cross-linking lag time of polyethylene, thereby solving the technical problem of premature cross-linking of the polyethylene composition during the rotational molding process of polyethylene; at present, in order to improve the cross-linking efficiency, a cross-linking promoter is usually added to the rotational molded cross-linked polyethylene. Although the cross-linking promoter can increase the degree of cross-linking, the degree of cross-linking is concentrated on the low molecular weight cross-linking promoter. When the material is subjected to an external force exceeding the critical force, the external force will be concentrated on the cross-linking promoter, causing the material to undergo brittle failure. Brittle failure will cause the rotational molded polyethylene products to be unable to be used in fields such as hydrogen storage bottles, wind power equipment, and large missile boxes that limit brittle failure. Summary of the invention

[0005] In order to overcome the problem of high brittleness of rotomoulded polyethylene products using crosslinking promoters in the prior art, the present invention provides a high-density cross-linked polyethylene rotomoulding material. The technical solution introduces high-pressure low-density polyethylene into high-density polyethylene to improve the toughness of the polyethylene, and then compounding a low-activity crosslinking agent with a high-activity crosslinking agent allows partial crosslinking of the low-activity crosslinking agent to occur in a targeted manner on the long chain of the low-density polyethylene, thereby further improving the toughness of the polyethylene and significantly improving the toughness of the rotomoulded cross-linked polyethylene.

[0006] The specific technical scheme of the present invention is: A high-density cross-linked polyethylene special material for rotational molding, the raw materials include, by mass percentage: High-density polyethylene 85-95%, Low density polyethylene 5-15%, Crosslinking agent 0.1~0.5%, Cross-linking accelerator 0.2~2%.

[0007] Preferably, the density of the high-density polyethylene is 0.940-0.970 g / cm 3 , the melt index of the high-density polyethylene is 5 to 30 g / 10 min.

[0008] Preferably, the density of the low-density polyethylene is 0.915-0.925 g / cm 3 , the melt index of the low-density polyethylene is 5 to 20 g / 10 min.

[0009] Preferably, the cross-linking agent comprises a low-activity cross-linking agent and a high-activity cross-linking agent in a mass ratio of 2 to 4:1.

[0010] Preferably, the low-activity cross-linking agent is di-tert-amyl peroxide.

[0011] Preferably, the highly active crosslinking agent is one or more of 2,5-(di-tert-butylperoxy)-2,5-dimethyl-3-hexyne, di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and tert-butyl isopropylbenzene peroxide.

[0012] Preferably, the cross-linking accelerator includes one or more of triallyl cyanurate, triallyl isocyanurate and diallyl phthalate.

[0013] Preferably, the cross-linking agent is a peroxide with a 10h half-life temperature greater than 110°C.

[0014] Preferably, the raw material further comprises an auxiliary agent with a mass fraction of 0.1 to 0.5%.

[0015] Preferably, the auxiliary agent is one or both of an antioxidant and a light stabilizer.

[0016] Preferably, the antioxidant is one or more of hindered phenol antioxidants and phosphite antioxidants.

[0017] Preferably, the light stabilizer is one or more of benzotriazole, benzophenone and triazine ultraviolet light absorbers.

[0018] The present invention provides a special material for rotational molding of high-density cross-linked polyethylene. The technical solution introduces high-pressure low-density polyethylene into high-density polyethylene to improve the toughness of the polyethylene. Then, low-activity cross-linking agents and high-activity cross-linking agents are used to make partial cross-linking targeted to occur on the long chains of the low-density polyethylene, further improving the toughness of the polyethylene and significantly improving the toughness of the rotationally molded cross-linked polyethylene.

[0019] Roto-molded cross-linked polyethylene usually uses various organic peroxides to produce free radicals by homolysis. Although the energy of free radicals is high, the energy level of each free radical is different. The different energy levels of free radicals determine their cross-linking efficiency and reaction type. Only reactions with reduced energy can proceed. For example, alkoxy free radicals can extract hydrogen from secondary carbon, but not from benzene. This is mainly because the energy of the former decreases, while the energy of the latter increases. Di-tert-amyl peroxide is a special low-activity cross-linking agent, mainly because it undergoes Beta cleavage after homolysis to generate vinyl free radicals. Vinyl free radicals have low activity and cannot extract secondary carbon hydrogen, but can provide tertiary carbon hydrogen and propylene hydrogen. Di-tert-amyl peroxide Due to the special property of the base, selective targeted cross-linking can be carried out; unlike high-density polyethylene, low-density polyethylene adopts a high-pressure process and ethylene polymerization is initiated by free radicals. Therefore, high-pressure low-density polyethylene generally has a high degree of branching and double bonds in its structure. Therefore, low-density polyethylene contains a certain number of tertiary hydrocarbons and propylene hydrogens. Combining the above principles, di-tert-amyl peroxide can selectively target cross-link low-density polyethylene. Therefore, low-density polyethylene plays the role of a cross-linking promoter to a certain extent. However, compared with ordinary low-molecular-weight cross-linking promoters, low-density polyethylene has a larger molecular weight, which can play a role of buffering and relaxation when subjected to external force. Therefore, it can effectively solve the problem of brittle cracking of rotational molded cross-linked materials.

[0020] A method for preparing the above-mentioned high-density cross-linked polyethylene rotational molding special material comprises the following steps: high-density polyethylene, low-density polyethylene, antioxidant, and light stabilizer are mixed evenly and then injected into a mixing device for blending; during the blending, a cross-linking agent and a cross-linking accelerator are injected into the mixing device for continued blending; after the blending is completed, extrusion granulation is performed to prepare the high-density cross-linked polyethylene rotational molding special material.

[0021] Preferably, the mixing device is a twin-screw mixing device, a single-screw extruder and a water mist eccentric pelletizing device.

[0022] Preferably, the conditions of the twin-screw extruder are: aspect ratio of 30-40:1, extrusion temperature of 110-140°C, and screw speed of 300-500r / min.

[0023] Preferably, the conditions of the single screw extruder are: aspect ratio 5-20:1, melt temperature 100-120°C.

[0024] Compared with the prior art, this application has the following technical effects: This technical solution introduces high-pressure low-density polyethylene into the high-density polyethylene blend to improve the toughness of the polyethylene, and then uses a combination of low-activity cross-linking agent and high-activity cross-linking agent to make partial cross-linking of the low-activity cross-linking agent targeted to the long chain of the low-density polyethylene, further improving the toughness of the polyethylene and significantly improving the toughness of the rotationally molded cross-linked polyethylene. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the embodiments.

[0026] Embodiment 1: A high-density cross-linked polyethylene rotomolding material, the raw materials include: 90% high-density polyethylene, the high-density polyethylene is HDPE8008, the density is 0.955g / cm 3 , melt index is 8g / 10min, PetroChina Dushanzi; 10% low-density polyethylene, low-density polyethylene is LDPE LC720, with a density of 0.922g / cm 3 , melt index is 9g / 10min, Mitsubishi, Japan; 0.2% cross-linking agent, the cross-linking agent is a low-activity cross-linking agent and a high-activity cross-linking agent in a ratio of 2:1, the low-activity cross-linking agent is di-tert-amyl peroxide, Arkema, France, and the high-activity cross-linking agent is tert-butyl isopropyl peroxide, Arkema, France; 1% cross-linking accelerator is tri-allyl cyanurate, Aladdin reagent; The balance is an auxiliary agent, which is an antioxidant and a light stabilizer. The antioxidant is a compound of a hindered phenol antioxidant and a phosphite antioxidant, and the light stabilizer is a benzotriazole, benzophenone or triazine ultraviolet light absorber.

[0027] A method for preparing the above-mentioned high-density cross-linked polyethylene rotational molding special material comprises the following steps: The main machine adopts a twin-screw mixer for blending and extrusion, a single-screw extruder and water mist eccentric pelletizing. High-density polyethylene and its composite, low-density polyethylene, antioxidant and light stabilizer oxidant are blended according to the above raw material ratios and fed into the mixing extruder for blending and extrusion. The crosslinking agent and the crosslinking accelerator are blended and injected into the vacuum port of the extruder using a high-precision weight loss scale metering feeder to extrude and granulate high-density cross-linked polyethylene rotational molding special material. The aspect ratio of the twin-screw extruder is 30-40:1, the extrusion temperature is 110-140°C, the screw speed is 300-500r / min, the aspect ratio of the single-screw extruder is 5-20:1, the extrusion temperature is 100-120°C, and the particle size of the high-density cross-linked polyethylene rotational molding special material is less than 30 meshes and the composition of less than 100 meshes is less than 20%.

[0028] Embodiment 2: A high-density cross-linked polyethylene rotomolding material, the raw materials include: 95% high-density polyethylene, the high-density polyethylene is HDPE8008, the density is 0.955g / cm 3 , melt index is 8g / 10min, PetroChina Dushanzi; 5% low-density polyethylene, low-density polyethylene is LDPE LC720, with a density of 0.922g / cm 3 , melt index is 9g / 10min, Mitsubishi, Japan; 0.2% cross-linking agent, the cross-linking agent is a low-activity cross-linking agent and a high-activity cross-linking agent in a ratio of 2:1, the low-activity cross-linking agent is di-tert-amyl peroxide, Arkema, France, and the high-activity cross-linking agent is tert-butyl isopropyl peroxide, Arkema, France; 1% cross-linking accelerator is tri-allyl cyanurate, Aladdin reagent; The balance is an auxiliary agent, which is an antioxidant and a light stabilizer. The antioxidant is a compound of a hindered phenol antioxidant and a phosphite antioxidant, and the light stabilizer is a benzotriazole, benzophenone or triazine ultraviolet light absorber.

[0029] A method for preparing the above-mentioned high-density cross-linked polyethylene rotational molding special material comprises the following steps: The main machine adopts a twin-screw mixer for blending and extrusion, a single-screw extruder and water mist eccentric pelletizing. High-density polyethylene and its composite, low-density polyethylene, antioxidant and light stabilizer oxidant are blended according to the above raw material ratios and fed into the mixing extruder for blending and extrusion. The crosslinking agent and the crosslinking accelerator are blended and injected into the vacuum port of the extruder using a high-precision weight loss scale metering feeder to extrude and granulate high-density cross-linked polyethylene rotational molding special material. The aspect ratio of the twin-screw extruder is 30-40:1, the extrusion temperature is 110-140°C, the screw speed is 300-500r / min, the aspect ratio of the single-screw extruder is 5-20:1, the extrusion temperature is 100-120°C, and the particle size of the high-density cross-linked polyethylene rotational molding special material is less than 30 meshes and the composition of less than 100 meshes is less than 20%.

[0030] Embodiment 3: A high-density cross-linked polyethylene rotomolding material, the raw materials include: 85% high-density polyethylene, the high-density polyethylene is HDPE8008, the density is 0.955g / cm 3 , melt index is 8g / 10min, PetroChina Dushanzi; 15% low-density polyethylene, low-density polyethylene is LDPE LC720, with a density of 0.922g / cm 3 , melt index is 9g / 10min, Mitsubishi, Japan; 0.2% cross-linking agent, the cross-linking agent is a low-activity cross-linking agent and a high-activity cross-linking agent in a ratio of 2:1, the low-activity cross-linking agent is di-tert-amyl peroxide, Arkema, France, and the high-activity cross-linking agent is tert-butyl isopropyl peroxide, Arkema, France; 1% cross-linking accelerator is tri-allyl cyanurate, Aladdin reagent; The balance is an auxiliary agent, which is an antioxidant and a light stabilizer. The antioxidant is a compound of a hindered phenol antioxidant and a phosphite antioxidant, and the light stabilizer is a benzotriazole, benzophenone or triazine ultraviolet light absorber.

[0031] A method for preparing the above-mentioned high-density cross-linked polyethylene rotational molding special material comprises the following steps: The main machine adopts a twin-screw mixer for blending and extrusion, a single-screw extruder and water mist eccentric pelletizing. High-density polyethylene and its composite, low-density polyethylene, antioxidant and light stabilizer oxidant are blended according to the above raw material ratios and fed into the mixing extruder for blending and extrusion. The crosslinking agent and the crosslinking accelerator are blended and injected into the vacuum port of the extruder using a high-precision weight loss scale metering feeder to extrude and granulate high-density cross-linked polyethylene rotational molding special material. The aspect ratio of the twin-screw extruder is 30-40:1, the extrusion temperature is 110-140°C, the screw speed is 300-500r / min, the aspect ratio of the single-screw extruder is 5-20:1, the extrusion temperature is 100-120°C, and the particle size of the high-density cross-linked polyethylene rotational molding special material is less than 30 meshes and the composition of less than 100 meshes is less than 20%.

[0032] Embodiment 4: A high-density cross-linked polyethylene rotomolding material, the raw materials include: 90% high-density polyethylene, the high-density polyethylene is HDPE8008, the density is 0.955g / cm 3 , melt index is 8g / 10min, PetroChina Dushanzi; 10% low-density polyethylene, low-density polyethylene is LDPE LC720, with a density of 0.922g / cm 3 , melt index is 9g / 10min, Mitsubishi, Japan; 0.1% cross-linking agent, the cross-linking agent is a 3:1 ratio of low-activity cross-linking agent and high-activity cross-linking agent, the low-activity cross-linking agent is di-tert-amyl peroxide, Arkema, France, and the high-activity cross-linking agent is tert-butyl isopropyl peroxide, Arkema, France; 1% cross-linking accelerator is tri-allyl cyanurate, Aladdin reagent; The balance is an auxiliary agent, which is an antioxidant and a light stabilizer. The antioxidant is a compound of a hindered phenol antioxidant and a phosphite antioxidant, and the light stabilizer is a benzotriazole, benzophenone or triazine ultraviolet light absorber.

[0033] A method for preparing the above-mentioned high-density cross-linked polyethylene rotational molding special material comprises the following steps: The main machine adopts a twin-screw mixer for blending and extrusion, a single-screw extruder and water mist eccentric pelletizing. High-density polyethylene and its composite, low-density polyethylene, antioxidant and light stabilizer oxidant are blended according to the above raw material ratios and fed into the mixing extruder for blending and extrusion. The crosslinking agent and the crosslinking accelerator are blended and injected into the vacuum port of the extruder using a high-precision weight loss scale metering feeder to extrude and granulate high-density cross-linked polyethylene rotational molding special material. The aspect ratio of the twin-screw extruder is 30-40:1, the extrusion temperature is 110-140°C, the screw speed is 300-500r / min, the aspect ratio of the single-screw extruder is 5-20:1, the extrusion temperature is 100-120°C, and the particle size of the high-density cross-linked polyethylene rotational molding special material is less than 30 meshes and the composition of less than 100 meshes is less than 20%.

[0034] Embodiment 5: A high-density cross-linked polyethylene rotomolding material, the raw materials include: 90% high-density polyethylene, the high-density polyethylene is HDPE8008, the density is 0.955g / cm 3 , melt index is 8g / 10min, PetroChina Dushanzi; 10% low-density polyethylene, low-density polyethylene is LDPE LC720, with a density of 0.922g / cm 3 , melt index is 9g / 10min, Mitsubishi, Japan; 0.3% cross-linking agent, the cross-linking agent is a 4:1 low-activity cross-linking agent and a high-activity cross-linking agent, the low-activity cross-linking agent is di-tert-amyl peroxide, Arkema, France, and the high-activity cross-linking agent is tert-butyl isopropyl peroxide, Arkema, France; 1% cross-linking accelerator is tri-allyl cyanurate, Aladdin reagent; The balance is an auxiliary agent, which is an antioxidant and a light stabilizer. The antioxidant is a compound of a hindered phenol antioxidant and a phosphite antioxidant, and the light stabilizer is a benzotriazole, benzophenone or triazine ultraviolet light absorber.

[0035] A method for preparing the above-mentioned high-density cross-linked polyethylene rotational molding special material comprises the following steps: The main machine adopts a twin-screw mixer for blending and extrusion, a single-screw extruder and water mist eccentric pelletizing. High-density polyethylene and its composite, low-density polyethylene, antioxidant and light stabilizer oxidant are blended according to the above raw material ratios and fed into the mixing extruder for blending and extrusion. The crosslinking agent and the crosslinking accelerator are blended and injected into the vacuum port of the extruder using a high-precision weight loss scale metering feeder to extrude and granulate high-density cross-linked polyethylene rotational molding special material. The aspect ratio of the twin-screw extruder is 30-40:1, the extrusion temperature is 110-140°C, the screw speed is 300-500r / min, the aspect ratio of the single-screw extruder is 5-20:1, the extrusion temperature is 100-120°C, and the particle size of the high-density cross-linked polyethylene rotational molding special material is less than 30 meshes and the composition of less than 100 meshes is less than 20%.

[0036] Embodiment 6: A high-density cross-linked polyethylene rotomolding material, the raw materials include: 90% high-density polyethylene, the high-density polyethylene is HDPE8008, the density is 0.955g / cm 3 , melt index is 8g / 10min, PetroChina Dushanzi; 10% low-density polyethylene, low-density polyethylene is LDPE LC720, with a density of 0.922g / cm 3 , melt index is 9g / 10min, Mitsubishi, Japan; 0.4% cross-linking agent, the cross-linking agent is a 2:1 low-activity cross-linking agent and a high-activity cross-linking agent, the low-activity cross-linking agent is di-tert-amyl peroxide, Arkema, France, and the high-activity cross-linking agent is 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexyne, Arkema, France; 1% cross-linking accelerator is triallyl cyanurate, Aladdin reagent; The balance is an auxiliary agent, which is an antioxidant and a light stabilizer. The antioxidant is a compound of a hindered phenol antioxidant and a phosphite antioxidant, and the light stabilizer is a benzotriazole, benzophenone or triazine ultraviolet light absorber.

[0037] A method for preparing the above-mentioned high-density cross-linked polyethylene rotational molding special material comprises the following steps: The main machine adopts a twin-screw mixer for blending and extrusion, a single-screw extruder and water mist eccentric pelletizing. High-density polyethylene and its composite, low-density polyethylene, antioxidant and light stabilizer oxidant are blended according to the above raw material ratios and fed into the mixing extruder for blending and extrusion. The crosslinking agent and the crosslinking accelerator are blended and injected into the vacuum port of the extruder using a high-precision weight loss scale metering feeder to extrude and granulate high-density cross-linked polyethylene rotational molding special material. The aspect ratio of the twin-screw extruder is 30-40:1, the extrusion temperature is 110-140°C, the screw speed is 300-500r / min, the aspect ratio of the single-screw extruder is 5-20:1, the extrusion temperature is 100-120°C, and the particle size of the high-density cross-linked polyethylene rotational molding special material is less than 30 meshes and the composition of less than 100 meshes is less than 20%.

[0038] Embodiment 7: A high-density cross-linked polyethylene rotomolding material, the raw materials include: 90% high-density polyethylene, the high-density polyethylene is HDPE8008, the density is 0.955g / cm 3 , melt index is 8g / 10min, PetroChina Dushanzi; 10% low-density polyethylene, low-density polyethylene is LDPE LC720, with a density of 0.922g / cm 3 , melt index is 9g / 10min, Mitsubishi, Japan; 0.5% cross-linking agent, the cross-linking agent is a 2:1 ratio of low-activity cross-linking agent and high-activity cross-linking agent, the low-activity cross-linking agent is di-tert-amyl peroxide, Arkema, France, and the high-activity cross-linking agent is di-tert-butyl peroxide, Arkema, France; 2% cross-linking accelerator is tri-allyl cyanurate, Aladdin reagent; The balance is an auxiliary agent, which is an antioxidant and a light stabilizer. The antioxidant is a compound of a hindered phenol antioxidant and a phosphite antioxidant, and the light stabilizer is a benzotriazole, benzophenone or triazine ultraviolet light absorber.

[0039] A method for preparing the above-mentioned high-density cross-linked polyethylene rotational molding special material comprises the following steps: The main machine adopts a twin-screw mixer for blending and extrusion, a single-screw extruder and water mist eccentric pelletizing. High-density polyethylene and its composite, low-density polyethylene, antioxidant and light stabilizer oxidant are blended according to the above raw material ratios and fed into the mixing extruder for blending and extrusion. The crosslinking agent and the crosslinking accelerator are blended and injected into the vacuum port of the extruder using a high-precision weight loss scale metering feeder to extrude and granulate high-density cross-linked polyethylene rotational molding special material. The aspect ratio of the twin-screw extruder is 30-40:1, the extrusion temperature is 110-140°C, the screw speed is 300-500r / min, the aspect ratio of the single-screw extruder is 5-20:1, the extrusion temperature is 100-120°C, and the particle size of the high-density cross-linked polyethylene rotational molding special material is less than 30 meshes and the composition of less than 100 meshes is less than 20%.

[0040] Embodiment 8: A high-density cross-linked polyethylene rotomolding material, the raw materials include: 90% high-density polyethylene, the high-density polyethylene is HDPE8008, the density is 0.955g / cm 3 , melt index is 8g / 10min, PetroChina Dushanzi; 10% low-density polyethylene, low-density polyethylene is LDPE LC720, with a density of 0.922g / cm 3 , melt index is 9g / 10min, Mitsubishi, Japan; 0.3% cross-linking agent, the cross-linking agent is a 2:1 low-activity cross-linking agent and a high-activity cross-linking agent, the low-activity cross-linking agent is di-tert-amyl peroxide, Arkema, France, and the high-activity cross-linking agent is 2,5-dimethyl-2,5-bis (tert-butyl peroxy) hexane, Arkema, France; 0.2% cross-linking accelerator is triallyl cyanurate, Aladdin reagent; The balance is an auxiliary agent, which is an antioxidant and a light stabilizer. The antioxidant is a compound of a hindered phenol antioxidant and a phosphite antioxidant, and the light stabilizer is a benzotriazole, benzophenone or triazine ultraviolet light absorber.

[0041] A method for preparing the above-mentioned high-density cross-linked polyethylene rotational molding special material comprises the following steps: The main machine adopts a twin-screw mixer for blending and extrusion, a single-screw extruder and water mist eccentric pelletizing. High-density polyethylene and its composite, low-density polyethylene, antioxidant and light stabilizer oxidant are blended according to the above raw material ratios and fed into the mixing extruder for blending and extrusion. The crosslinking agent and the crosslinking accelerator are blended and injected into the vacuum port of the extruder using a high-precision weight loss scale metering feeder to extrude and granulate high-density cross-linked polyethylene rotational molding special material. The aspect ratio of the twin-screw extruder is 30-40:1, the extrusion temperature is 110-140°C, the screw speed is 300-500r / min, the aspect ratio of the single-screw extruder is 5-20:1, the extrusion temperature is 100-120°C, and the particle size of the high-density cross-linked polyethylene rotational molding special material is less than 30 meshes and the composition of less than 100 meshes is less than 20%.

[0042] Comparative Example 1: Compared with Example 1, only high-density polyethylene was used in Comparative Example 1, and the other conditions were the same as those in Example 1.

[0043] Comparative Example 2: Compared with Example 1, the cross-linking agent in Comparative Example 2 does not include a low-activity cross-linking agent, and the other conditions are the same as those in Example 1.

[0044] Comparative Example 3: Compared with Example 1, the ratio of the low-activity cross-linking agent to the high-activity cross-linking agent in Comparative Example 3 is 1:1, and the other conditions are the same as those in Example 1.

[0045] Comparative Example 4: Compared with Example 1, the ratio of the low-activity cross-linking agent to the high-activity cross-linking agent in Comparative Example 4 is 6:1, and the other conditions are the same as those in Example 1.

[0046] Test example: The high-density cross-linked polyethylene roto-molding special materials prepared in the above Examples 1 to 8 and Comparative Examples 1 to 4 were made into roto-molded polyethylene products, and the brittle and toughness properties of the roto-molded polyethylene were tested. The test method was "Reference GB / T 39933-2021 Roto-molding Low Temperature Impact Test", and the test results are shown in Table 1; Table 1 Test results As shown in Table 1, the impact strength of the rotomolded polyethylene products obtained in Examples 1 to 8 is 24-30 J / mm, and the brittle toughness is in the range of 8 ductility / 2 brittleness to 10 ductility / 0 brittleness, showing excellent impact strength and toughness.

[0047] The raw material of the rotational molded product of Comparative Example 1 only uses high-density polyethylene, and its impact strength is only 12 J / mm, and the brittle toughness is 2 elongated / 8 brittle. Compared with Comparative Example 1, the rotational molded products of Examples 1 to 8 have significantly higher impact strength than Comparative Example 1, significantly higher toughness than Comparative Example 1, and significantly lower brittleness than Comparative Example 1. It can be seen that the rotational molded products made of the high-density cross-linked polyethylene rotational molding special material of the present invention have the characteristics of high impact strength and high toughness.

[0048] The raw material of the rotational molded product of Comparative Example 2 does not contain a low-activity cross-linking agent, and its impact strength is 17 J / mm, and its toughness is 4 ductile / 6 brittle. From the results of Comparative Examples 1 and 2, it can be seen that adding low-density polyethylene to high-density polyethylene can improve the toughness of the rotational molded product, but compared with Examples 1 to 8 of the present invention, the toughness and impact strength of the rotational molded product of Comparative Example 2 without adding a low-activity cross-linking agent are still significantly lower than those of the rotational molded products of Examples 1 to 8 of the present invention.

[0049] In addition, Comparative Examples 3 and 4 analyzed the usage ratios of low-activity cross-linking agents and high-activity cross-linking agents, respectively. The results showed that low-activity cross-linking agents and high-activity cross-linking agents need to be used in appropriate ratios to enable the rotationally molded products to have high toughness and high impact strength. If the ratio of low-activity cross-linking agents is too low, the toughness and impact strength of the rotationally molded products cannot be significantly improved. If the ratio of low-activity cross-linking agents is too high, the impact strength and toughness of the rotationally molded products will be significantly reduced, making the product unusable.

[0050] 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-density cross-linked polyethylene rotational molding material, characterized in that: The raw materials include by mass percentage: High density polyethylene 85~95%, Low density polyethylene 5~15%, Crosslinking agent 0.1~0.5%, Cross-linking accelerator 0.2~2%.

2. A high-density cross-linked polyethylene rotational molding material according to claim 1, characterized in that: The density of the high-density polyethylene is 0.940-0.970 g / cm 3 , the melt index of the high-density polyethylene is 5 to 30 g / 10min; The density of the low-density polyethylene is 0.915-0.925 g / cm 3 , the melt index of the low-density polyethylene is 5~20g / 10min.

3. A high-density cross-linked polyethylene rotational molding material according to claim 1, characterized in that: The cross-linking agent comprises a low-activity cross-linking agent and a high-activity cross-linking agent in a mass ratio of 2 to 4:1; The low-activity cross-linking agent is di-tert-amyl peroxide; The highly active cross-linking agent is one or more of 2,5-(di-tert-butylperoxy)-2,5-dimethyl-3-hexyne, di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and tert-butyl isopropylbenzene peroxide; The cross-linking accelerator includes one or more of triallyl cyanurate, triallyl isocyanurate and diallyl phthalate.

4. A high-density cross-linked polyethylene rotational molding material according to claim 1 or 3, characterized in that: The cross-linking agent is a peroxide with a 10 h half-life temperature greater than 110°C.

5. A high-density cross-linked polyethylene rotational molding material according to claim 1, characterized in that: The raw materials also include auxiliary agents with a mass fraction of 0.1-0.5%.

6. A high-density cross-linked polyethylene rotomolding material according to claim 5, characterized in that: The auxiliary agent is one or two of an antioxidant and a light stabilizer; The antioxidant is one or more of hindered phenol antioxidants and phosphite antioxidants; The light stabilizer is one or more of benzotriazole, benzophenone and triazine ultraviolet light absorbers.

7. A method for preparing a high-density cross-linked polyethylene rotomolding material according to any one of claims 1 to 6, characterized in that: The high-density polyethylene, low-density polyethylene, antioxidant and light stabilizer are mixed evenly and injected into a mixing device for blending. During the blending, the cross-linking agent and the cross-linking accelerator are injected into the mixing device for continuous blending. After the blending is completed, the high-density cross-linked polyethylene special rotational molding material is extruded and granulated.

8. The preparation method according to claim 7, characterized in that: The mixing device comprises a twin-screw mixing device, a single-screw extrusion device and a water mist eccentric pelletizing device.

9. The preparation method according to claim 8, characterized in that: The conditions of the twin-screw extruder are: aspect ratio of 30-40:1, extrusion temperature of 110-140°C, and screw speed of 300-500 r / min.

10. The preparation method according to claim 8, characterized in that: The conditions of the single screw extruder are: aspect ratio 5-20:1, melt temperature 100-120°C.

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