A dynamically crosslinked polyethylene and a method of making and using the same
By grafting disulfide monomers onto polyethylene segments to form a reversible cross-linked network, the problems of reprocessing and recycling performance of polyethylene materials are solved, realizing dynamically cross-linked polyethylene with high tensile strength and high storage modulus, which is suitable for recycling.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- KINGFA SCI & TECH CO LTD
- Filing Date
- 2026-03-16
- Publication Date
- 2026-05-29
AI Technical Summary
Existing polyethylene materials cannot be remelted after cross-linking, resulting in resource waste. Furthermore, the mechanical properties of existing dynamically cross-linked polyethylene deteriorate after recycling, making it difficult to simultaneously possess high tensile strength and high storage modulus.
By grafting disulfide monomers onto polyethylene segments to form a reversible dynamic crosslinking network, dynamic crosslinked polyethylene is prepared by reacting ethylene copolymers containing maleic anhydride units with disulfide monomers. Antioxidants and light stabilizers are then combined to improve the material properties.
This technology enables polyethylene materials to retain high tensile strength and high storage modulus after recycling. The materials can be reprocessed and reused, with a high retention rate of mechanical properties, making them suitable for recycling.
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Figure CN122103414A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of polymer materials technology, and in particular to a dynamically cross-linked polyethylene, its preparation method, and its application. Background Technology
[0002] Polyethylene (PE) is one of the most widely used general-purpose plastics, possessing excellent chemical stability and processing properties, and is widely used in the manufacture of pipes, films, cables, and other products. However, PE's strength, resistance to environmental stress cracking, and creep resistance are relatively poor, limiting its application in structural components. To improve the strength and creep resistance of PE, industrial processes employ crosslinking technologies such as peroxide crosslinking and radiation crosslinking to construct a stable three-dimensional network structure between PE molecular chains, forming crosslinked polyethylene (XLPE). However, the crosslinking linkage in XLPE is irreversible covalent bonding. This permanent crosslinking structure prevents the material from being remelted and processed, hindering the recycling and reuse of polyethylene, leading to resource waste.
[0003] To address the aforementioned issues, dynamic chemical bonds such as β-hydroxy ester bonds, borate ester bonds, disulfide bonds, and imine bonds are introduced into the molecular structure to construct dynamic three-dimensional networks. These networks enhance material strength and resistance to environmental stress cracking while also providing recyclability and reprocessing capabilities. For example, patent CN112358631A provides a dynamic covalent crosslinked material. This material is prepared by transesterifying linear polyethylene with borate ester groups with a borate ester crosslinking agent to create a dynamically crosslinked polymer containing borate ester bonds. This polymer is then added to commercially available polyethylene to prepare a polyethylene / dynamically crosslinked polyethylene composite material. This composite material exhibits significantly enhanced mechanical properties, solvent resistance, and creep resistance.
[0004] Although there are literature reports on research into dynamically cross-linked polyethylene, exploration into how to prepare it efficiently and easily is very limited. Furthermore, existing dynamically cross-linked polyethylene is prone to cross-linking point destruction after recycling, leading to a decline in its mechanical properties. No reports have been found on the preparation of recyclable dynamically cross-linked polyethylene that simultaneously possesses high tensile strength, high storage modulus, and high performance retention after recycling. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a dynamically cross-linked polyethylene that has both high storage modulus and high tensile strength. Its cross-linking bonds can undergo reversible breakage and recombination, and it retains high mechanical properties after recycling.
[0006] Another object of the present invention is to provide a method for preparing dynamically cross-linked polyethylene.
[0007] Another object of the present invention is to provide a recyclable cross-linked polyethylene plastic comprising the dynamically cross-linked polyethylene.
[0008] The above-mentioned objective of this invention is achieved through the following technical solution:
[0009] This invention protects a dynamically cross-linked polyethylene, the raw material of which comprises the following components in parts by weight: 94-100 parts of ethylene copolymer containing maleic anhydride (MAH) units, 0.3-5 parts of disulfide monomer; The disulfide monomer is a polyamino disulfide compound; The MAH content in the ethylene copolymer containing MAH units is ≥2.8wt%.
[0010] The method for testing the MAH content in the ethylene copolymer containing MAH units is Fourier transform infrared spectroscopy (FTIR) analysis.
[0011] Preferably, the content of the ethylene copolymer containing MAH units that satisfies the purpose of the present invention can be a range of 94 parts, 95 parts, 96 parts, 97 parts, 98 parts, 99 parts and 100 parts or any two of them.
[0012] The ethylene copolymer containing MAH units accounts for no less than 90% by mass of the dynamically cross-linked polyethylene, preferably no less than 95%.
[0013] Preferably, the content of the disulfide monomer that satisfies the purpose of the present invention can be one or any two of the following: 0.3 parts, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts and 5 parts.
[0014] In one embodiment, the disulfide monomer is a polyamino aromatic disulfide; preferably, the disulfide monomer is selected from at least one of 4,4-dithiodiphenylamine, 2,2-dithiodiphenylamine, or cystamine.
[0015] In one embodiment, the molar ratio of the anhydride group to the amino group of the disulfide monomer in the MAH-containing ethylene copolymer is (2-10):1; preferably, the molar ratio is (2.5-7):1.
[0016] Preferably, the molar ratio of the anhydride group to the amino group of the disulfide monomer in the MAH-containing ethylene copolymer is one or any two of the following: 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1 and 10:1.
[0017] The ethylene copolymer containing MAH units described in this invention can be selected from random copolymers containing ethylene and MAH units and / or polyethylene grafted with maleic anhydride.
[0018] In some embodiments, the ethylene copolymer containing MAH units is an ethylene-alkyl acrylate (C1-C4) ester-maleic anhydride terpolymer, including but not limited to ethylene-methyl acrylate-maleic anhydride terpolymer and ethylene-butyl acrylate-maleic anhydride terpolymer; preferably, in the ethylene-alkyl acrylate-maleic anhydride copolymer containing MAH units, the alkyl acrylate content is 5-20 wt%, and the MAH content is 2.8-6 wt%. More preferably, the MAH content is 3.1-6 wt%.
[0019] In one embodiment, the ethylene copolymer containing MAH units has a melt flow rate of 5-15 g / 10 min at 190°C and a load of 2.16 kg. The melt flow rate is tested according to ISO 1133-1-2022.
[0020] The dynamically cross-linked polyethylene of the present invention can be supplemented with commonly used additives in the art. In one embodiment, the dynamically cross-linked polyethylene of the present invention further includes: 0.1-2 parts of additives; the additives are at least one of antioxidants and light stabilizers.
[0021] Preferably, the additives are: 0.1-0.8 parts of antioxidant and 0.1-0.8 parts of light stabilizer.
[0022] Optionally, the antioxidant includes a primary antioxidant and a combination of a primary antioxidant and a secondary antioxidant; the primary antioxidant is selected from at least one of hindered phenolic antioxidants, amine antioxidants, hydroxylamine antioxidants, or benzofuranone antioxidants; specifically, the primary antioxidant may be selected from antioxidant 1790, antioxidant 1010, antioxidant 1076, or antioxidant 264. The secondary antioxidant includes phosphite antioxidants or thioester antioxidants; specifically, the secondary antioxidant may be selected from antioxidant 168, antioxidant 626, antioxidant DLTDP, or antioxidant DSTDP.
[0023] Optionally, the light stabilizer may be selected from hindered amine light stabilizers, such as light stabilizer T-81.
[0024] This invention protects a method for preparing dynamically cross-linked polyethylene, comprising the following steps: mixing raw material components in the prescribed amounts and performing intensive mixing, allowing the ethylene copolymer containing MAH units to react with disulfide monomers in a molten state, and pressing and molding to obtain the dynamically cross-linked polyethylene.
[0025] In one embodiment, the mixing temperature is 160~180℃ and the mixing time is 15~20min.
[0026] In one embodiment, the pressing process includes hot pressing and cold pressing; the hot pressing temperature is 180~190℃, the hot pressing time is 5~7min, and the pressure is 5~10MPa; the cold pressing temperature is 30~40℃, the cold pressing time is 3~5min, and the pressure is 5~10MPa.
[0027] This invention protects a recyclable cross-linked polyethylene plastic comprising the dynamically cross-linked polyethylene.
[0028] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a dynamically crosslinked polyethylene. By reacting an ethylene copolymer containing MAH units with a disulfide monomer, dynamically crosslinkable disulfide groups are grafted onto the PE chain segments, forming a crosslinked network in the polyethylene system. This allows the material to simultaneously possess high storage modulus and high tensile strength. Furthermore, the crosslinked network of disulfide bonds can undergo reversible breaking and recombination under specific conditions, enabling the polyethylene to be reprocessed and recycled. The recycled polyethylene still possesses excellent tensile strength. Attached Figure Description
[0029] Figure 1 The infrared absorption spectra of dynamically cross-linked polyethylene in Comparative Example 1 and Example 1 of this invention are shown. Detailed Implementation
[0030] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way.
[0031] The experimental methods in the following examples and comparative examples, where specific conditions are not specified, are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market.
[0032] The reagents used in the various embodiments and comparative examples of this invention are as follows: Ethylene copolymers containing MAH units: EAM 1#: Ethylene-butyl acrylate-maleic anhydride terpolymer; butyl acrylate content is 6.5wt%, MAH content is 3.6wt%. Melt flow rate (ISO 1133-1-2022) is 8~12 g / 10min at 190℃ and 2.16 Kg load; SK functional polymer, 4210.
[0033] EAM 2#: Ethylene-methyl acrylate-maleic anhydride terpolymer; methyl acrylate content is 15wt%, MAH content is 3.1wt%. Melt flow rate (ISO 1133-1-2022) is 6~8g / 10min at 190℃ and 2.16 Kg load; SK functional polymer, 3430.
[0034] PE-g-MAH: Maleic anhydride-grafted polyethylene, grafting rate 0.7wt%; grade: MC218; manufacturer: Ningbo Nengzhiguang New Material Technology Co., Ltd.
[0035] E-BA-GMA terpolymer: ethylene-butyl acrylate-glycidyl methacrylate terpolymer; acrylate content is 25wt%, GMA content is 5wt%. At 190℃ and 2.16 kg load, its melt flow rate (ISO 1133-1-2022) is 10~15 g / 10 min; AX8750, SK functional polymer.
[0036] Disulfide monomers: 4,4-Dithiodiphenylamine: Shanghai Maclean Biochemical Technology Co., Ltd.
[0037] 2,2-Dithiodiphenylamine: Shanghai Maclean Biochemical Technology Co., Ltd.
[0038] Antioxidants: Antioxidant 1010 and Antioxidant 168 in a mass ratio of 1:1.
[0039] The following examples and comparative methods for preparing dynamically cross-linked polyethylene include the following steps: After mixing all raw materials evenly, the mixture is added to a Hacker torque rheometer for intensive mixing at a temperature of 160℃ and a screw speed of 50 rpm for 15 minutes. Following intensive mixing, the resulting material is subjected to hot and cold pressing using a flat vulcanizing apparatus. The hot pressing temperature is 180℃ for 5 minutes, and the cold pressing temperature is 40℃ for 3 minutes. The pressure used in both hot and cold pressing is 10 MPa. After cold pressing, the material is removed to obtain the final product.
[0040] Examples 1-6 and Comparative Examples 1-5 A series of dynamically cross-linked polyethylenes are provided, the raw materials of which, by weight, are shown in Table 1. In Comparative Example 5, the molar ratio between the GMA groups and the amino groups of the disulfide monomer in the E-BA-GMA terpolymer is 3:1.
[0041] Table 1
[0042] Performance testing The dynamic crosslinked polyethylene of each embodiment and comparative example was characterized and its performance tested as follows: 1. Infrared absorption spectroscopy characterization The polyethylene samples from Example 1 and Comparative Example 1 were tested in the mid-infrared region (4000-400 cm⁻¹). -1 ) to perform infrared absorption spectroscopy (FTIR) testing.
[0043] The results are as follows Figure 1 As shown in the FTIR spectrum, the EAM of Comparative Example 1 is at 1781 cm⁻¹. -1 The region exhibits the characteristic infrared absorption peak of acid anhydrides at 1734 cm⁻¹. -1 and 1234cm -1 The infrared absorption peak at 3399 cm⁻¹ is characteristic of the ester group. The product of the reaction between EAM and 4,4-dithiodiphenylamine in Example 1 shows an infrared absorption peak at 3399 cm⁻¹. -1 The infrared characteristic peak of the -OH group in the carboxyl group was formed, and in addition, at 1781 cm⁻¹... -1 The intensity of the characteristic infrared absorption peak of the acid anhydride at 1589 cm⁻¹ decreased significantly, and at 1589 cm⁻¹... -1 Characteristic absorption peaks of the benzene ring were observed. The results demonstrate that the anhydride of EAM and the amino group of 4,4-dithiodiphenylamine reacted in Example 1 of this invention.
[0044] 2. Rheological and mechanical property testing The dynamically cross-linked polyethylenes prepared in each embodiment and comparative example were subjected to the following tests, and the results are shown in Table 2.
[0045] Storage modulus: The storage modulus was obtained by using a rotational viscometer in accordance with the test method of standard GB / T 33061.10-2016.
[0046] Viscosity: Tested according to the standard GB / T 33061.10-2016, at a test temperature of 25℃.
[0047] Tensile strength after recycling: Refer to standard GB / T1040.3-2006, Determination of Tensile Properties of Plastics. The tensile strength after three recycling cycles was measured. The recycling steps were as follows: the molded sample was cut into pieces, and then subjected to hot and cold pressing again using a flat vulcanizing apparatus. The hot pressing temperature was 180℃, and the hot pressing time was 5 minutes; the cold pressing temperature was 40℃, and the cold pressing time was 3 minutes. The pressure used in both hot and cold pressing was 10 MPa. After cold pressing, the sample was removed, and the cycle was repeated three times.
[0048] Table 2
[0049] As shown in Table 2, the preparation method of the present invention yields dynamically cross-linked polyethylene with high mechanical properties and excellent recyclability, retaining high tensile strength even after three recycling cycles. Specifically, the dynamically cross-linked polyethylene has a tensile strength ≥17.2 MPa, viscosity ≥13417 Pa·s, storage modulus ≥1120 Pa, tensile strength ≥17.0 MPa after three recycling cycles, and tensile strength retention rate not less than 90% after three recycling cycles.
[0050] Comparing Examples 1-4 with Comparative Example 1 or Comparative Example 5 with Comparative Example 2, it can be seen that the viscosity and mechanical properties of the present invention are significantly improved after the addition of disulfide monomers, proving the formation of a cross-linked network structure. Furthermore, the high tensile strength is still maintained after three recycling cycles, indicating that the cross-links can undergo reversible breakage and recombination, demonstrating good recyclability.
[0051] Comparative Examples 3-4 show that when the maleic anhydride content in the polyethylene system is low, a cross-linked network structure cannot be effectively formed, resulting in limited improvement in tensile strength and storage modulus.
[0052] In Comparative Example 5, a dynamically cross-linked polyethylene was prepared using a polyethylene copolymer containing GMA and a disulfide monomer. Its mechanical properties decreased significantly after multiple recyclings, and the tensile strength retention rate was only 60.5% after three recyclings.
[0053] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A dynamically cross-linked polyethylene, characterized in that, The raw materials consist of the following components in parts by weight: 94-100 parts of ethylene copolymer containing MAH units, 0.3-5 parts of disulfide monomer; The disulfide monomer is a polyamino disulfide compound; The MAH content in the ethylene copolymer containing MAH units is ≥2.8wt%.
2. The dynamically cross-linked polyethylene according to claim 1, characterized in that, The disulfide monomer is a polyamino aromatic disulfide; preferably, the disulfide monomer is selected from at least one of 4,4-dithiodiphenylamine and 2,2-dithiodiphenylamine.
3. The dynamically cross-linked polyethylene according to claim 1, characterized in that, The molar ratio of the anhydride group to the amino group of the disulfide monomer in the ethylene copolymer containing MAH units is (2-10):1; preferably, the molar ratio is (2.5-7):
1.
4. The dynamically cross-linked polyethylene according to claim 1, characterized in that, The ethylene copolymer containing MAH units is an ethylene-alkyl acrylate-maleic anhydride copolymer, with an alkyl acrylate content of 5-20 wt% and an MAH content of 3-6 wt%.
5. The dynamically cross-linked polyethylene according to claim 1, characterized in that, The ethylene copolymer containing MAH units has a melt mass flow rate of 5~15 g / 10min at 190℃ and 2.16 Kg load.
6. The dynamically cross-linked polyethylene according to claim 1, characterized in that, Also includes: 0.1-2 parts of additives; the additives are selected from at least one of antioxidants and light stabilizers.
7. A method for preparing dynamically cross-linked polyethylene according to any one of claims 1-6, characterized in that, The process includes the following steps: mixing the raw material components in the specified amounts and then mixing them thoroughly, allowing the ethylene copolymer containing MAH units to react with the disulfide monomer in a molten state, and then pressing and molding the mixture to obtain the dynamically cross-linked polyethylene.
8. The method for preparing dynamically cross-linked polyethylene according to claim 7, characterized in that, The mixing temperature is 160~180℃, and the mixing time is 15~20min.
9. The method for preparing dynamically cross-linked polyethylene according to claim 7, characterized in that, The pressing process includes hot pressing and cold pressing; the hot pressing temperature is 180~190℃, the hot pressing time is 5~7min, and the pressure is 5~10MPa; the cold pressing temperature is 30~40℃, the cold pressing time is 3~5min, and the pressure is 5~10MPa.
10. A recyclable cross-linked polyethylene plastic, characterized in that, It includes the dynamically cross-linked polyethylene as described in any one of claims 1-6.