Polyethylene wax with reversible crosslinking characteristic as well as preparation method and application thereof

Abstract

The invention relates to polyethylene wax with a reversible crosslinking characteristic and a preparation method and application thereof, and relates to the field of polymer functional aids and processing and application thereof. The polyethylene wax with the reversible cross-linking characteristic is prepared from three monomers of furyl ethylene, maleimide ethylene and ethylene through double-bond addition copolymerization, and the number-average molecular weight is 1000-100000. The polyethylene wax provided by the invention can be used as a flow modifier during polyethylene material processing and a cross-linking modifier during use. The low molecular weight polyethylene wax can reduce the energy consumption of processing equipment and increase the flatness of the product. And meanwhile, the reversible crosslinking of furan and maleimide groups on the chain segment can endow the resin with thermoset property in use and thermoplastic cycle processability after use.

Description

Technical Field

[0001] This invention relates to the field of polymer functional additives and their processing and application, specifically to a polyethylene wax with reversible crosslinking properties, its preparation method, and its application. Background Technology

[0002] Polyethylene is a widely used polymer material in daily life, but its molecular chains have poor heat / creep resistance, low mechanical properties, poor resistance to environmental stress cracking, and insufficient electrical insulation properties. Therefore, its products generally require cross-linking modification to meet usage requirements. Currently, industrial methods commonly use ultraviolet irradiation, peroxides, and silane coupling agents to cross-link polyethylene. This method forms a permanent three-dimensional network structure between polyethylene molecular chains, improving the performance of polyethylene products, but it cannot endow them with the ability to be recycled after damage, resulting in significant environmental pollution and resource waste.

[0003] Patent (ZL202010215821.2) provides a cross-linked polyethylene and its preparation method and application based on the Diels-Alder reversible reaction. In this system, the maleimide cross-linking agent is an inorganic small molecule incompatible with the polyethylene bulk. During processing, problems arise such as an imbalance in the molar ratio of furan / maleimide groups, uneven mixing or inability to achieve uniform mixing at the molecular level, and migration and precipitation of the small molecule cross-linking agent. Furthermore, the high melt viscosity of polyethylene easily leads to excessive energy consumption in equipment and rough product surfaces during processing, generally requiring the addition of flow modifiers. Summary of the Invention

[0004] In view of the shortcomings of the above-mentioned technologies, the present invention provides a polyethylene wax with reversible crosslinking properties, its preparation method and application, which solves the problems of environmental pollution and resource waste caused by the non-recyclability of existing crosslinked polyethylene products, the dispersion problem of small molecule maleimide crosslinking agents in the polyethylene system in existing Diels-Alder reversible crosslinking (uneven dispersion will lead to uneven crosslinking, some places are over-crosslinked while some are not crosslinked, and they are not on the molecular chain, the distance cannot be guaranteed, and the degree of crosslinking is insufficient) and diffusion precipitation problem (precipitation will affect subsequent crosslinking and cause surface contact toxicity), as well as the problems of increased energy consumption and rough products caused by poor fluidity during polyethylene processing and modification.

[0005] To achieve the above objectives, the present invention mainly provides the following technical solutions: This invention provides a polyethylene wax with reversible crosslinking properties, the structural formula of which is as follows:

[0006] Where x = 1~1000, y = 1~3000, z = 1~1000; R1 is one of -H, -NO2, -CHO, -COOH, -CO-CH3, or -CH=CH-COCH3; R2 is one of -H, -CH3, -CHO, or -COOCH3; R3 is one of -H, -CH3, or -COOCH3; R4 is one of -CH2 or -C6H6-; Preferably, the ratio of x to z is (0.1~10):1.

[0007] Preferably, the polyethylene wax is low molecular weight polyethylene. The number average molecular weight of the polyethylene wax is 1,000 to 100,000, more preferably 5,000 to 80,000, and even more preferably 20,000 to 50,000.

[0008] Preferably, the polyethylene wax is prepared by copolymerization of three monomers: furanylethylene, maleimide-based ethylene, and ethylene. Copolymerization is a conventional ethylene polymerization method; controlling the proportions of each group and the molecular weight to meet the requirements of polyethylene wax is sufficient. The polyethylene wax of this invention requires the addition of ethylene as a third copolymer monomer, which can adjust the molecular weight and other properties of the polyethylene wax, making it more compatible with the polyolefin matrix without phase separation.

[0009] The molecular chain of furanylethylene monomers simultaneously contains an addition-polymerizable vinyl group and a subsequently reversibly reacting furan group. Furanylethylene monomers include, but are not limited to, one or more of 2-vinylfuran, 2-furanacrylaldehyde, 4-(2-furanyl)-3-buten-2-one, 2-furanacrylic acid, and 2-(prop-1-yn-2-yl)furan, and their derivatives. The furanylethylene monomer is preferably 2-vinylfuran or 2-furanacrylic acid, or a mixture thereof.

[0010] Maleimide-based vinyl monomers contain both addition-polymerizable vinyl groups and subsequently reversibly reactive maleimide groups. Maleimide-based vinyl monomers include, but are not limited to, one or more of N-(4-vinylphenyl)maleimide, N-allylmaleimide, and their derivatives. Preferably, the maleimide-based vinyl monomer is N-(4-vinylphenyl)maleimide or N-allylmaleimide, or a mixture thereof.

[0011] Preferably, x = 50~500, y = 200~2000, z = 50~500, and the ratio of x to z is (0.5~2):12.

[0012] The present invention also provides a method for preparing the polyethylene wax with reversible crosslinking properties, comprising the following steps: simultaneously adding ethylene monomer, furanylethylene monomer and maleimide-based ethylene monomer and corresponding polymerization aids to a reaction vessel for copolymerization reaction, controlling the copolymerization reaction conditions to make the number average molecular weight between 1000 and 100000, thereby obtaining the polyethylene wax with reversible crosslinking properties.

[0013] Preferably, the molar ratio of ethylene monomer, furanylethylene monomer, and maleimide-based ethylene monomer is 100:3~10:3~10, and more preferably 100:3~7:3~7.

[0014] Preferably, the number-average molecular weight is controlled between 5,000 and 80,000. More specifically, the number-average molecular weight is between 20,000 and 50,000.

[0015] The copolymerization process can be one of three methods: Method 1, Method 2, or Method 3. Method 1 involves the following steps: ethylene monomer, furanylethylene monomer, and maleimide-based ethylene monomer are introduced into a reaction vessel according to the ratio of polyethylene wax. A molecular weight regulator is introduced, and a catalyst is added. After the reaction, polyethylene wax particles are obtained.

[0016] Method 2 involves the following steps: adding solvent to the reactor, heating and replacing the air inside the reactor, then introducing ethylene monomer, furanylethylene monomer, and maleimide-based ethylene monomer into the reactor according to the ratio of polyethylene wax, so that the reaction system reaches the predetermined pressure, then adding catalyst to the reactor to initiate the polymerization reaction, and obtaining polyethylene wax particles after continuous stirring.

[0017] Method 3 involves the following steps: adding a diluent to the polymerization reactor, then heating the reactor to replace the air inside, adding ethylene monomer, maleimide-based ethylene monomer, and furanyl-based ethylene monomer according to the proportion of polyethylene wax, and introducing a molecular weight regulator. The reaction system reaches the predetermined pressure, and finally, a catalyst is added to initiate the polymerization reaction. The mixture is continuously stirred to obtain polyethylene wax particles.

[0018] Preferably, in Method 1, the molecular weight regulator is hydrogen gas with a concentration of 80-120 ppm. The catalyst includes a main catalyst and a co-catalyst, with the main catalyst having a concentration of 80-120 ppm and the co-catalyst having a concentration of 40-60 ppm. The main catalyst is a chromium-based catalyst, and the co-catalyst is a triethylaluminum catalyst. The reaction temperature is controlled at 80-90°C, the pressure is maintained at 1.5-2.5 MPa, and the reaction time is 4-6 h.

[0019] Preferably, in method two, the solvent includes one or more of n-hexane, pentane, isobutane, propane, cyclohexane, heptane, octane, and petroleum ether. The heating temperature is 110-130°C. Air replacement in the reactor is achieved by nitrogen replacement. The predetermined pressure is 1-2 MPa. The catalyst includes a main catalyst and a co-catalyst, with the concentration of the main catalyst being 80-120 ppm and the concentration of the co-catalyst being 80-120 ppm. The main catalyst is a zirconium-based metallocene catalyst, and the co-catalyst is a methylaluminoxane catalyst. The stirring time is 4-6 hours.

[0020] Preferably, in method three, the diluent is isopentane. The heating temperature is 45-55°C. The molecular weight regulator is hydrogen, with a concentration of 80-120 ppm. The predetermined pressure is 0.8-1.2 MPa. The catalyst includes a main catalyst and a co-catalyst, with the main catalyst concentration being 80-120 ppm and the co-catalyst concentration being 45-55 ppm. The main catalyst is a titanium-based catalyst, and the co-catalyst is triethylaluminum. The stirring time is 4-6 hours.

[0021] The copolymerization process includes three conventional ethylene polymerization methods: high-pressure free radical polymerization, medium-pressure polymerization, and low-pressure coordination polymerization. Specifically, traditional polyethylene polymerization methods such as slurry polymerization, suspension polymerization, and gas-phase polymerization can be selected. Different raw materials have different boiling points and can be added by vaporization through pressurization or heating.

[0022] Preferably, the present invention employs high-pressure free radical polymerization or low-pressure coordination polymerization, and specifically adopts slurry polymerization or suspension polymerization processes.

[0023] The copolymerization reaction conditions include one or more of the following: reaction temperature, reaction pressure, reaction time, type and content of chain initiator, chain transfer agent, and chain terminator.

[0024] The present invention also provides a gas-phase preparation method for the polyethylene wax with reversible crosslinking properties, comprising the following steps: Ethylene, 2-vinylfuran, and N-allylmaleimide were introduced into a reaction vessel in the proportion of polyethylene wax. Hydrogen gas (80-120 ppm) was introduced as a molecular weight regulator. A chromium-based main catalyst (80-120 ppm) and a triethylaluminum co-catalyst (40-60 ppm) were added. The reaction temperature was controlled at 80-90℃ and the pressure was maintained at 1.5-2.5 MPa. After reacting for 4-6 hours, polyethylene wax particles were obtained.

[0025] The present invention also provides a solution method for preparing the polyethylene wax with reversible crosslinking properties, comprising the following steps: Hexane was added to the reactor as a solvent, the temperature was raised to 110-130°C, and the air in the reactor was replaced with nitrogen. Ethylene, 2-vinylfuran, and N-allylmaleimide were then introduced into the reactor according to the proportion of polyethylene wax to bring the reaction system to a predetermined pressure of 1-2 MPa. Then, a zirconium-based metallocene catalyst (80-120 ppm) and a methylaluminoxane co-catalyst (80-120 ppm) were added to the reactor to initiate the polymerization reaction. After stirring for 4-6 hours, polyethylene wax particles were obtained.

[0026] The present invention also provides a slurry method for preparing the polyethylene wax with reversible crosslinking properties, comprising the following steps: Isopentane diluent was added to the polymerization reactor, and the reactor temperature was set to 45-55°C. Nitrogen gas was introduced to replace the air in the reactor. Ethylene, N-allylmaleimide, and 2-vinylfuran were added according to the proportion of polyethylene wax, and hydrogen gas (80-120 ppm) was introduced. The reaction system reached a predetermined pressure of 0.8-1.2 MPa. Finally, a titanium-based catalyst (80-120 ppm) and triethylaluminum co-catalyst (45-55 ppm) were added to initiate the polymerization reaction. The mixture was stirred continuously for 4-6 hours to obtain polyethylene wax particles. The present invention also provides the application of the polyethylene wax with reversible crosslinking properties in the modification of matrix materials with polyolefin backbone. The application is in the areas of flow modification and / or reversible crosslinking modification.

[0027] Preferably, the matrix material with polyolefin as the backbone is polyethylene or polypropylene.

[0028] Preferably, the polyethylene includes one or more of high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ultra-high molecular weight polyethylene.

[0029] Preferably, the polyethylene modification is achieved by mixing polyethylene, the polyethylene wax of the present invention, and functional additives, followed by injection molding, extrusion, and granulation.

[0030] The amount of polyethylene wax with reversible crosslinking properties is 0.5% to 3% of the matrix material, preferably 0.8% to 1.2%.

[0031] The functional additives are one or more of the following: antioxidants, nucleating agents, whitening agents, and lubricants.

[0032] This invention also provides a method for preparing modified polyethylene, comprising the following steps: Polyethylene, the polyethylene wax of this invention, and functional additives are mixed and then granulated by injection molding using a screw extruder to obtain modified polyethylene (a modified material modified with polyethylene wax).

[0033] Preferably, the amount of polyethylene wax with reversible crosslinking properties added is 0.5% to 3%, more preferably 0.8% to 1.2%.

[0034] Preferably, the temperature range for injection molding extrusion granulation is 120~200℃.

[0035] Preferably, the screw speed is 100~200 rpm, and the feed screw speed is 10~30 kg / h.

[0036] This invention also provides an application of modified polyethylene in cross-linked polyethylene cables, polyethylene film bags, polyethylene injection molded products, polyethylene fiber products, and polyethylene foam products.

[0037] This invention obtains products with reversible cross-linking properties by processing materials through molding processes such as injection molding, vacuum forming, blown film, wire drawing, and foaming.

[0038] The present invention also provides a method for recycling the modified polyethylene, comprising the following steps: heating the product prepared from the modified polyethylene to 150~220℃, remelting it, and remolding it to prepare a new product.

[0039] The polyethylene wax of this invention, when mixed with polyethylene, reacts with the furan and maleimide groups in the wax upon cooling. This reaction locks in conventional long-chain polyethylene, allowing linear polyethylene molecular chains to form a cross-linked network structure, thus imparting better solvent resistance, heat resistance, mechanical properties, and creep resistance. Upon heating, the furan and maleimide groups break down, and the cross-linking is reversible. At temperatures above a certain value (>90℃, e.g., 130℃), the cross-linking bonds break, allowing for remelting and reheating to form the final product. Conventional cross-linked materials are neither soluble nor meltable and must be discarded after destruction. The addition of the polyethylene wax of this invention transforms thermosetting materials into thermoplastic ones, giving them thermoplastic properties.

[0040] Existing technologies use two groups of bismaleimide to lock the furan groups on the polyethylene side chains. However, this approach suffers from problems such as the precipitation of polar bismaleimide from the non-polar polyethylene matrix (especially noticeable during heating and melting) and uneven dispersion of the bismaleimide additive. Furthermore, directly using these functional additives to make products is too costly and impractical. Additionally, furan and maleimide on the same chain segment can crosslink at the molecular level, an effect that existing technologies, even with excellent mixing, cannot achieve.

[0041] Compared with the prior art, the present invention has the following beneficial effects: (1) The applications of the polyethylene wax provided by this invention include its use as a flow modifier during the processing of polyethylene materials and as a crosslinking modifier during use. Low molecular weight polyethylene wax can reduce the energy consumption of processing equipment and increase the smoothness of the product. At the same time, the reversible crosslinking of furan and maleimide groups on the chain segments can endow it with thermosetting properties during use and thermoplastic cycle processing properties after use.

[0042] (2) When used, the polyethylene wax of the present invention exhibits thermosetting properties: better solvent resistance and heat resistance (heat distortion temperature), mechanical properties (greater strength and modulus, shorter elongation), creep resistance, and aging resistance. During processing, it can be used as a lubricant to reduce energy consumption and surface roughness. After use, it can be remelted and processed to prepare products, which has the effect of reducing environmental pollution and reducing usage costs. Attached Figure Description

[0043] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the cross-linked structure of the polyethylene wax with reversible cross-linking properties prepared in Example 1. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0045] The polyethylene wax of this invention possesses reversible crosslinking properties and is prepared by double bond addition copolymerization of three monomers: furanylethylene, maleimide-ethylene, and ethylene, with a molecular weight ranging from 1,000 to 100,000. The polyethylene wax provided by this invention can be used as a flow modifier during polyethylene material processing and as a crosslinking modifier during use. Low molecular weight polyethylene wax can reduce energy consumption in processing equipment and increase the smoothness of the finished product. Simultaneously, the reversible crosslinking of furan and maleimide groups on the chain segments imparts thermosetting properties during use and thermoplastic recyclability after use.

[0046] The preparation method of the modified polyethylene of the present invention is as follows: (1) Weigh a certain amount of commercially available polyethylene, add appropriate amounts of antioxidants, nucleating agents, whitening agents, lubricants, opening agents, flame retardants and other functional additives, and then add 0.1wt%~10wt% of the polyethylene wax with reversible crosslinking properties provided by this invention, shake well and set aside.

[0047] (2) Turn on the twin-screw extruder and clean the machine. Set the appropriate temperature for each temperature zone, ranging from 60 to 250°C. Start the experiment half an hour after the temperature stabilizes.

[0048] (3) Add the above-mixed material to the hopper, turn on the screw main unit (20~400rpm), and turn on the feeding screw (1~100kg / h).

[0049] (4) The material is extruded by an extruder, water-cooled into strips, granulated, dried and packaged to obtain the modified material of polyethylene wax with reversible cross-linking characteristics of the present invention.

[0050] (5) The material obtained in step (4) is subjected to molding processes such as injection molding, vacuum forming, blown film, wire drawing, and foaming to obtain a product with reversible cross-linking characteristics.

[0051] The polyethylene wax of the present invention has the following cross-linked structure: Figure 1 As shown. When polyethylene wax is mixed with polyethylene and other materials, the furan and maleimide groups in the same or different polyethylene waxes react upon cooling, which can lock in conventional long-chain polyethylene and cause linear polyethylene molecular chain segments to form a cross-linked network structure.

[0052] Example 1: Polymerization of polyethylene wax with reversible crosslinking properties via gas phase (a) 2-Vinylfuran, N-allylmaleimide, and ethylene monomer (99.9%) are subjected to rigorous purification to remove any possible impurities such as moisture and alcohols. Chromium-based supported catalysts require prior activation treatment, with triethylaluminum used as a co-catalyst and hydrogen (99.99%) as a molecular weight regulator.

[0053] (b) A small amount of nitrogen gas is first injected into the reactor to replace the air and prevent impurities such as oxygen from interfering with the polymerization reaction. 1 mol of pretreated ethylene, 0.05 mol of 2-vinylfuran, 0.05 mol of N-allylmaleimide, and 100 ppm of hydrogen are introduced into a gas-phase polymerization reactor equipped with a stirrer in a specific ratio. The reaction temperature is controlled at 85°C, and the pressure is maintained at 2.0 MPa.

[0054] (c) The activated chromium-based main catalyst (100 ppm) and triethylaluminum co-catalyst (50 ppm) are added to the reactor through a specific feeding device. The gas-liquid mixture in the reactor is continuously stirred to ensure that the components are in full contact and that the reaction proceeds uniformly.

[0055] (d) After 4 hours, the reaction was stopped, the polyethylene particles were removed, dissolved in toluene at 80°C to remove unreacted monomers and residual catalysts and other impurities, poured into cold ethyl acetate to precipitate, and dried to obtain a pure polyethylene wax product with reversible crosslinking properties (number average molecular weight 11500).

[0056] Example 2: Polymerization of polyethylene wax with reversible crosslinking properties via solution method (a) Ethylene: Deeply purified to a purity of 99.95% or higher. n-Hexane: 99% purity, dried before use. Comonomers: N-allylmaleimide and 2-vinylfuran undergo rigorous purification to remove any possible impurities such as moisture and alcohols. A zirconium-based metallocene catalyst with high catalytic activity and selectivity is selected, with methylaluminoxane (MAO) as a cocatalyst.

[0057] (b) An oxygen-free reaction environment was created by replacing the air in the reactor with nitrogen. In a reactor equipped with a stirrer and temperature control device, 1000 ml of dried and purified n-hexane was first added as a solvent. Then, the reactor was heated to 120°C, and 1 mol of ethylene, 0.05 mol of 2-vinylfuran, and 0.05 mol of N-allylmaleimide were sequentially introduced into the reactor to bring the reaction system to a predetermined pressure of 1.5 MPa.

[0058] (c) Next, the zirconium-based metallocene catalyst (100 ppm) and methylaluminoxane (100 ppm) are mixed in an appropriate ratio and added to the reactor to initiate the polymerization reaction. (d) After stirring for 4 hours, the reaction was stopped. The hexane solvent was removed by distillation, and the polyethylene particles were taken out and dissolved in toluene at 80°C to remove unreacted monomers and residual catalysts and other impurities. The mixture was poured into cold ethyl acetate to precipitate and dried to obtain a pure polyethylene wax product with reversible crosslinking properties (number average molecular weight 9300).

[0059] Example 3: Polymerization of polyethylene wax with reversible crosslinking properties via slurry method (a) Ethylene monomers are purified by molecular sieve adsorption to achieve a purity of over 99.95%. Hydrogen purity is 99.99%. The comonomers N-allylmaleimide and 2-vinylfuran undergo rigorous purification to remove any possible impurities such as moisture and alcohols. A titanium-based main catalyst is used in combination with a triethylaluminum cocatalyst. Isopentane with a purity of 99% is selected as a diluent, and it is dried and purified before use.

[0060] (b) Add the treated isopentane diluent to the polymerization reactor, then set the temperature of the polymerization reactor to 50°C and purge the air in the reactor with nitrogen. (c) 1 mol of ethylene, 0.05 mol of N-allyl maleimide, 0.05 mol of 2-vinylfuran and 100 ppm of hydrogen were added sequentially to the polymerization reactor, and the reaction system reached the predetermined pressure of 1.0 MPa.

[0061] (d) Add 100 ppm of titanium-based catalyst and 50 ppm of triethylaluminum co-catalyst to the polymerization reactor to initiate the polymerization reaction. (e) Continue stirring for 4 hours, discharge the slurry containing polyethylene particles from the polymerization reactor, filter, send the obtained polyethylene particles to the washing tower, wash repeatedly with fresh diluent, and dry to obtain a pure polyethylene wax product with reversible cross-linking properties (number average molecular weight 9800).

[0062] Table 1. Physical properties of polyethylene waxes with reversible crosslinking characteristics

[0063] Example 4 (1) Weigh 100 parts of commercially available polyethylene powder, add 0.5 parts of antioxidant 1010 and 0.3 parts of antioxidant 168, add 1.0 part of polyethylene wax from Example 1, and shake to mix evenly.

[0064] (2) Add it to a twin-screw extruder for melt blending. The temperature of each section of the screw is 90~200℃, the speed is 150rpm, and the feed screw is 10rpm.

[0065] (3) After the melt is discharged from the die head, it goes through water cooling, strip drawing, pelletizing and drying processes.

[0066] (4) The modified material obtained is used as a special material for medium and low voltage cables to coat copper wires to prepare medium and low voltage cables.

[0067] The heat resistance temperature of the resulting cable-specific material increased from 70.2℃ to 87.5℃, the tensile strength increased from 23.2MPa to 31.9MPa, and the elastic modulus increased from 950MPa to 1790MPa.

[0068] The modified polyethylene product was heated to 180℃, remelted, and reshaped to produce a new product. Its heat resistance temperature still reached 86.9℃, tensile strength reached 31.7MPa, and elastic modulus reached 1786MPa.

[0069] Example 5 (1) Weigh 100 parts of commercially available polyethylene powder, add 0.5 parts of antioxidant 1010 and 0.3 parts of antioxidant 168, add 1.0 part of polyethylene wax from Example 2, and shake to mix evenly.

[0070] (2) Add it to a twin-screw extruder for melt blending. The temperature of each section of the screw is 90~200℃, the speed is 150rpm, and the feed screw is 10rpm.

[0071] (3) After the melt is discharged from the die head, it goes through water cooling, strip drawing, pelletizing and drying processes.

[0072] (4) The modified material is blown into film bags for application.

[0073] The tensile strength of the resulting membrane bag increased from 21.4 MPa to 32.6 MPa, the elastic modulus increased from 930 MPa to 1680 MPa, and the elongation at break decreased from 280% to 170%. The stiffness and load-bearing capacity were significantly improved, allowing for thinner fabrics to be made while ensuring usability.

[0074] Example 6 (1) Weigh 100 parts of commercially available polyethylene powder, add 0.5 parts of antioxidant 1010 and 0.3 parts of antioxidant 168, add 1.0 part of polyethylene wax from Example 3, and shake to mix evenly.

[0075] (2) Add it to a twin-screw extruder for melt blending. The temperature of each section of the screw is 90~200℃, the speed is 150rpm, and the feed screw is 10rpm.

[0076] (3) After the melt is discharged from the die head, it goes through water cooling, strip drawing, pelletizing and drying processes.

[0077] (4) The obtained modified material is rotomolded into industrial ton barrels.

[0078] The tensile strength of the resulting rotational molding increased from 22.9 MPa to 36.7 MPa, and the elastic modulus increased from 950 MPa to 1870 MPa. The corrosion resistance to polar solvents such as toluene, benzene, carbon tetrachloride, and gasoline was significantly improved at 70°C.

[0079] Comparative Example 1 (1) Furan-based polyethylene wax was prepared without the addition of vinyl maleimide, following the procedure of Example 2.

[0080] (2) Weigh 100 parts of commercially available polyethylene powder, add 0.5 parts of antioxidant 1010 and 0.3 parts of antioxidant 168, add 1.0 parts of furanyl polyethylene wax, and then add 1,6-dimaleimide hexane (BMH) of the corresponding number of functional groups as a crosslinking agent, and shake to mix evenly.

[0081] (2) Add it to a twin-screw extruder for melt blending. The temperature of each section of the screw is 90~200℃, the speed is 150rpm, and the feed screw is 10rpm.

[0082] (3) After the melt is discharged from the die head, it goes through water cooling, strip drawing, pelletizing and drying processes.

[0083] (4) The obtained modified material is blown into a film bag.

[0084] The tensile strength of the resulting membrane bag increased from 21.4 MPa to 24.6 MPa, the elastic modulus increased from 930 MPa to 1130 MPa, and the elongation at break decreased from 280% to 240%. The comparison results show that the fact that the two functional groups are not located on the same molecule leads to a significant decrease in the degree of crosslinking, and the improvement in crosslinking performance is not significant.

[0085] Comparative Example 2 (equal amounts of polyfuranyl ethylene and polymaleimide ethylene were directly mixed) The preparation method is similar to that in Examples 1 and 4, except that the polyethylene wax is replaced with an equal amount of raw materials to prepare a mixture of polyfuran-based ethylene (polymerized from 0.5 mol ethylene and 0.05 mol 2-vinylfuran) and polymaleimide-based ethylene (polymerized from 0.5 mol ethylene and 0.05 mol N-allylmaleimide).

[0086] The heat resistance temperature of the resulting cable-specific material increased from 70.2℃ to 76.9℃, the tensile strength increased from 23.2MPa to 26.7MPa, and the elastic modulus increased from 950MPa to 1250MPa.

[0087] The modified polyethylene product is heated to 180℃, remelted, and then reshaped to produce a new product. Its heat resistance temperature is 75.2℃, tensile strength is 21.5 MPa, and elastic modulus is 1190 MPa.

[0088] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A polyethylene wax having reversible crosslinking properties, characterized in that, The polyethylene wax with reversible cross-linking property has the following structural formula: Wherein, x=1~1000, y=1~3000, z=1~1000; R1 is one of -H, -NO2, -CHO, -COOH, -CO-CH3, -CH=CH-COCH3; R2 is one of -H, -CH3, -CHO, -COOCH3; R3 is one of -H, -CH3, -COOCH3; R4 is one of -CH2-, -C6H6-.

2. The polyethylene wax having reversible crosslinking properties according to claim 1, characterized in that, The polyethylene wax is prepared by copolymerization of furan-based ethylene, maleimide-based ethylene and ethylene.

3. The polyethylene wax having reversible crosslinking properties according to claim 2, wherein, The furan-based ethylene monomer contains both addition polymerizable vinyl group and subsequent reversible furan group; And / or, the maleimide-based ethylene monomer contains both addition polymerizable vinyl group and subsequent reversible maleimide group.

4. The polyethylene wax having reversible crosslinking properties according to claim 3, characterized in that, The furan-based ethylene monomer includes one or more of 2-vinyl furan, 2-furan propylene aldehyde, 4-(2-furan)-3-buten-2-ketone, 2-furan propylene acid, 2-(prop-1-alkyne-2-yl) furan and derivatives thereof; And / or, the maleimide-based ethylene monomer includes one or more of N-(4-vinyl phenyl) maleimide, N-allyl maleimide and derivatives thereof.

5. A process for the preparation of the polyethylene wax as claimed in claim 1, characterized in that, The method comprises the following steps: adding ethylene monomer, furan-based ethylene monomer and maleimide-based ethylene monomer and corresponding polymerization aids into a reaction kettle for copolymerization, and controlling the copolymerization conditions to make the number average molecular weight be 1000~100000, thereby obtaining the polyethylene wax with reversible cross-linking property.

6. The method of claim 5, wherein the polyethylene wax is prepared by a process comprising: The copolymerization method includes one of method one, method two and method three; The steps of method one are as follows: introducing ethylene monomer, furan-based ethylene monomer and maleimide-based ethylene monomer into a reaction kettle according to the proportion of polyethylene wax, introducing molecular weight regulator, adding catalyst, and obtaining polyethylene wax particles after reaction; The steps of method two are as follows: adding solvent into a reaction kettle, heating and replacing air in the kettle, introducing ethylene monomer, furan-based ethylene monomer and maleimide-based ethylene monomer into the reaction kettle according to the proportion of polyethylene wax, making the reaction system reach a predetermined pressure, adding catalyst into the reaction kettle to initiate polymerization, and obtaining polyethylene wax particles after continuous stirring; The steps of method three are as follows: adding diluent into a polymerization kettle, then heating the polymerization kettle, replacing air in the kettle, adding ethylene monomer, maleimide-based ethylene monomer and furan-based ethylene monomer according to the proportion of polyethylene wax, introducing molecular weight regulator, making the reaction system reach a predetermined pressure, finally adding catalyst to initiate polymerization, and obtaining polyethylene wax particles after continuous stirring.

7. Application of the polyethylene wax with reversible cross-linking property in claim 1 in modification of matrix material with polyolefin as skeleton.

8. A method for producing a modified polyethylene, characterized by, The method comprises the following steps: Mixing polyethylene, polyethylene wax in claim 1 and functional aids, and granulating by screw extruder, thereby obtaining modified polyethylene.

9. The use of the modified polyethylene prepared by the method of claim 8 in crosslinked polyethylene cables, polyethylene film bags, polyethylene injection molded articles, polyethylene fiber articles, polyethylene foamed articles.

10. The recycling process of the modified polyethylene according to claim 8, wherein the modified polyethylene is a modified polyethylene obtained by the process according to any one of claims 1 to 7. Step: the product prepared by the modified polyethylene is heated to 150-220℃, remelted, and then reshaped to prepare a new product.

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