Polyethylene elastomer as well as preparation method and application thereof

Abstract

The invention discloses a polyethylene elastomer and a preparation method and application thereof, the polyethylene elastomer is a copolymer of ethylene, first olefin and second olefin, the light transmittance is greater than 88.5%, the haze is greater than 15%, the total molar content of the first olefin and the second olefin in the polyethylene elastomer accounts for 3.0-10.0 mol%, and the total molar content of the second olefin accounts for 1.0-10.0 mol%. The first olefin is alpha-olefin with an odd number of carbon atoms greater than 4, the second olefin is alpha-olefin with an even number of carbon atoms greater than 3, the weight ratio of the first olefin to the second olefin in the polyethylene elastomer is 0.8-3.0, after the polyethylene elastomer is subjected to continuous self-nucleation annealing, the average lamellar thickness of the polyethylene elastomer is 2.0-3.6 nm, and the average lamellar thickness of the polyethylene elastomer is 2.0-3.6 nm. And does not contain a portion having an average lamellar thickness of 4.0 nm or more. According to the polyethylene elastomer provided by the invention, the ethylene is copolymerized with the alpha-olefin of which the carbon atom number is greater than 4 and is an odd number and the alpha-olefin of which the carbon atom number is greater than 3 and is an even number, so that the polyethylene elastomer with high light transmittance and high haze is prepared, and the requirement on a polyethylene film in a high-end application scene can be met.

Description

Technical Field

[0001] This invention relates to the field of copolymer technology, and more specifically to a polyethylene elastomer, its preparation method, and its application. Background Technology

[0002] Polyethylene (PE) film is widely used in packaging, agriculture, electronics, and other fields due to its low cost and ease of processing. In particular, optical films, which combine high light transmittance and low haze, are high-end functional materials mainly used in diffusion films in LCD backlight modules, sensor layers in touch screens, smart greenhouse covering films (dimming films), smart dimming glass films, building skylights and awning films, soft light diffusion films, and high-end packaging films.

[0003] Currently, conventional methods for improving the haze of polyethylene films mainly include adding inorganic fillers (such as calcium carbonate and silicon dioxide) or increasing the spherulite size through crystallization control to enhance the light scattering effect. However, these traditional techniques have significant drawbacks: on the one hand, the introduction of inorganic fillers increases the light scattering interface, which, while improving haze, often leads to a significant decrease in transmittance, typically failing to reach above 70%, and easily causing poor optical uniformity; on the other hand, filler particles are prone to agglomeration in the matrix, forming stress concentration points, severely weakening the tensile strength and toughness of the film, resulting in a decrease in mechanical properties of up to 30% to 50%. In addition, the large spherulite structure obtained by controlling crystallization also exacerbates light reflection and scattering, reduces transmittance, and may affect the material's ductility and tear resistance.

[0004] Therefore, existing polyethylene films cannot achieve a synergistic optimization of high haze and high transmittance, as there is a clear mutual exclusion between the two, accompanied by a deterioration in mechanical properties. Thus, how to balance the transmittance and haze of polyethylene film materials is a problem that urgently needs to be solved. Summary of the Invention

[0005] This disclosure aims to address the problems existing in the prior art by providing a polyethylene elastomer, its preparation method, and its application.

[0006] According to a first aspect of this disclosure, a polyethylene elastomer is provided, wherein the polyethylene elastomer is a copolymer of ethylene and a first olefin and a second olefin, the polyethylene elastomer has a light transmittance > 88.5% and a haze > 15%, the total molar content of the first olefin and the second olefin in the polyethylene elastomer is 3.0-10.0 mol%, wherein the first olefin is an α-olefin with more than 4 carbon atoms and an odd number of carbon atoms, the second olefin is an α-olefin with more than 3 carbon atoms and an even number of carbon atoms, the weight ratio of the first olefin and the second olefin in the polyethylene elastomer is 0.8-3.0, and after continuous self-nucleation annealing, the average lamellar thickness of the polyethylene elastomer is 2.0-3.6 nm, and it does not contain any portion with an average lamellar thickness greater than 4.0 nm.

[0007] In one embodiment of this disclosure, the first olefin is selected from 1-pentene, 1-heptene, 1-nonene, and 1-undecene.

[0008] In one embodiment of this disclosure, the second olefin is selected from one of 1-butene, 1-hexene, 1-octene, and 1-decene.

[0009] In one embodiment of this disclosure, the combination of the first olefin and the second olefin is one of 1-pentene / 1-butene, 1-pentene / 1-hexene, 1-pentene / 1-octene, 1-pentene / 1-decene, 1-heptene / 1-butene, 1-heptene / 1-hexene, 1-heptene / 1-octene, 1-heptene / 1-decene, 1-nonene / 1-butene, 1-nonene / 1-hexene, 1-nonene / 1-octene, and 1-nonene / 1-decene.

[0010] In one embodiment of this disclosure, the density of the polyethylene elastomer is 0.865-0.895 g / cm³. 3 The weight-average molecular weight is 50,000-270,000 g / mol, the molecular weight distribution is 1.5-6.0, the melting point is 50-100℃, and the melt index is 0.05-10.0 g / 10min.

[0011] According to a second aspect of this disclosure, a method for preparing a polyethylene elastomer is provided, comprising the following steps: S1: The first olefin and the second olefin are mixed in a certain proportion to form a first mixture; S2: Add the polymerization solvent and the first mixture in S1 to the reactor to form a second mixture, then add the co-catalyst to the reactor, and charge the reactor with ethylene until the pressure inside the reactor reaches the predetermined polymerization pressure, then raise the temperature and stabilize it at the predetermined polymerization temperature; S3: Inject the catalyst into the reactor of S2 and maintain the pressure inside the reactor at the predetermined polymerization pressure. After reacting for 10-15 minutes, discharge the material, collect the polyethylene elastomer, dry it, and weigh it.

[0012] In one embodiment of this disclosure, the catalyst is one or more of a metallocene catalyst, a post-transition metal catalyst, and a non-metallocene catalyst, and the central metal element of the catalyst is selected from Ti, Zr, Hf, Cr, Fe, Co, and Ni.

[0013] In one embodiment of this disclosure, the co-catalyst is selected from one or more of methylaluminoxane, modified methylaluminoxane, tri(pentafluorophenyl)borane, borate, triethylaluminum, triisobutylaluminum, and trihexylaluminum.

[0014] In one embodiment of this disclosure, the polymerization solvent is selected from one or more of n-hexane, cyclohexane, n-heptane, 2-methylhexane, 3-methylhexane, isoalkanes Isopar C, and isoalkanes Isopar E.

[0015] In one embodiment of this disclosure, the predetermined polymerization temperature is 100-180°C, the predetermined polymerization pressure is 2.0-5.0 MPa, and the weight ratio of the first olefin and the second olefin in the first mixture is 0.5-3.0.

[0016] According to a third aspect of this disclosure, an application of a polyethylene elastomer in modified polyethylene, polypropylene, and engineering plastics is provided.

[0017] According to a fourth aspect of this disclosure, an application of a polyethylene elastomer in the preparation of optical thin films is provided.

[0018] The present disclosure provides a polyethylene elastomer, its preparation method, and its application. By copolymerizing ethylene with α-olefins having an odd number of carbon atoms (greater than 4) and α-olefins having an even number of carbon atoms (greater than 3), a polyethylene elastomer with both high light transmittance and high haze is obtained. This polyethylene elastomer can be used for the modification of polyethylene, polypropylene, and engineering plastics. The modified polyethylene and polypropylene samples show significantly improved impact strength and high toughness, thus meeting the requirements for high puncture resistance in film applications.

[0019] In addition, this polyethylene elastomer can also be used to prepare optical films. The resulting film products have the characteristics of high light transmittance, high haze, high toughness and good light diffusion, which can meet the requirements of polyethylene films in high-end application scenarios.

[0020] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the present disclosure and, together with their description, serve to explain the principles of the present disclosure.

[0022] Figure 1 This is a flowchart of a method for preparing a polyethylene elastomer provided in one embodiment of the present disclosure. Detailed Implementation

[0023] To make the inventive objectives, technical solutions, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with specific embodiments. It should be understood that the embodiments described in this specification are merely illustrative and not intended to limit the scope of this application.

[0024] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an unspecified range.

[0025] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or more" means two or more.

[0026] The foregoing description of this invention is not intended to describe every disclosed embodiment or implementation. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are merely representative and should not be construed as exhaustive.

[0027] First, the nouns and terms used in one or more embodiments will be explained.

[0028] Successive Self-nucleation / Annaling (SSA) is a thermal classification analysis technique commonly used to analyze polyethylene and its copolymers. It uses a series of continuous heating, holding, and cooling cycles to reveal the molecular structure characteristics of the material, particularly the distribution of short-chain branches. SSA results in different melting peaks, and the crystal size can be calculated from the temperatures corresponding to these peaks. Simply put, each heating step melts only the least perfect crystals with the lowest melting point, while retaining the most perfect crystals with the highest melting point as "nucleating agents." It can "classify" molecular chains based on their chemical composition (comonomer content) and sequence length. Each partial melting step in SSA essentially "screens" the molecular chains: at a given Ta temperature, only long chain segments that can form crystals with melting points higher than Ta are retained. Short chain segments containing more comonomers can only crystallize at lower temperatures.

[0029] Isopar C and Isopar E are two types of isoparaffin solvents produced by ExxonMobil, differing primarily in the number of carbon atoms. Isopar C: Carbon number 10-12, distillation range 98-104℃, density 0.698 g / cm³, flash point below 0℃. Isopar E: Carbon number 12-14, distillation range 105-125℃, density 0.78 kg / dm³, flash point 63℃.

[0030] Lamellar crystals are a basic microscopic crystal structure unit in semi-crystalline polymers (such as polyethylene and polypropylene). They are layered structures formed by the folding and arrangement of polymer molecular chains. The thinner the lamellar crystals, the less perfect the crystal development and the lower the crystallinity.

[0031] Polyethylene (PE) film is widely used due to its low cost and excellent processing performance. With the expansion of high-end applications, not only are good mechanical properties required, but also higher demands are placed on its optical properties, especially the special optical balance between high light transmittance and low haze. These functional films are widely used in diffusion films in LCD backlight modules, touchscreen sensor layers, smart greenhouse dimming films, building skylights, diffused light films, and high-end packaging.

[0032] However, traditional polyethylene films often face the problem of significantly reduced light transmittance while achieving high haze, and the two are mutually restrictive. Conventional methods enhance light scattering and improve haze by adding inorganic fillers (such as CaCO3 and SiO2) or promoting the formation of large spherulites, but the large number of interfaces introduced by this will cause severe light loss and stress concentration, resulting in light transmittance that is usually below 70%, accompanied by a 30% to 50% decrease in tensile strength and a deterioration in toughness.

[0033] In existing technologies, some high-haze films utilize polyethylene / polypropylene blends, leveraging the difference in crystallization behavior between the two phases to enhance scattering. While this achieves high haze, it remains difficult to improve light transmittance. In summary, overcoming the performance contradiction between light transmittance and haze in polyethylene films, and achieving efficient light scattering while maintaining high transmittance, remains a key technical challenge in the current development of functional optical films.

[0034] This disclosure addresses the problems existing in the prior art by providing a polyethylene elastomer, its preparation method, and its applications. The polyethylene elastomer is a copolymer of ethylene with a first olefin and a second olefin. The first olefin is selected from 1-pentene, 1-heptene, 1-nonene, and 1-undecene, and the second olefin is selected from 1-butene, 1-hexene, 1-octene, and 1-decene. The combination of the first and second olefins can be one of 1-pentene / 1-butene, 1-pentene / 1-hexene, 1-pentene / 1-octene, 1-pentene / 1-decene, 1-heptene / 1-butene, 1-heptene / 1-hexene, 1-heptene / 1-octene, 1-heptene / 1-decene, 1-nonene / 1-butene, 1-nonene / 1-hexene, 1-nonene / 1-octene, or 1-nonene / 1-decene. The polyethylene elastomer obtained thereby has a density of 0.865-0.895 g / cm³. 3 The weight-average molecular weight is 50,000-270,000 g / mol, the molecular weight distribution is 1.5-6.0, the melting point is 50-100℃, the melt index is 0.05-10.0 g / 10min, the light transmittance is >88.5%, the haze is >15%, and the total molar content of the first and second olefins in the polyethylene elastomer is 3.0-10.0 mol.

[0035] In this copolymer, the first olefin is an α-olefin with more than 4 carbon atoms and an odd number of carbon atoms, and the second olefin is an α-olefin with more than 3 carbon atoms and an even number of carbon atoms. The weight ratio of the first olefin and the second olefin in the polyethylene elastomer is 0.8-3.0. After continuous self-nucleation annealing, the average lamellar thickness of the polyethylene elastomer is 2.0-3.6 nm, and it does not contain any part with an average lamellar thickness of more than 4.0 nm. Since the thinner the lamellar, the less perfect the crystal development and the lower the crystallinity, the copolymer molecular chains are more likely to form small and imperfect microcrystals during crystallization. The interfacial area between crystals and amorphous materials per unit volume (i.e., the total area of ​​scattering centers) is greatly increased. Moreover, due to the variety of branch types, the interface is no longer a smooth and clear boundary, but a diffuse, rough region with more dramatic changes in refractive index gradient. This complex interfacial structure has a much higher scattering efficiency for light than a smooth interface, thereby improving the scattering behavior between crystal planes and increasing its haze, resulting in a haze >15%. Furthermore, because the microcrystals are much smaller, the light transmittance does not decrease, resulting in the film still exhibiting high light transmittance.

[0036] like Figure 1 As shown, this disclosure provides a method for preparing a polyethylene elastomer, comprising the following steps: S1: The first olefin and the second olefin are mixed in a certain proportion to form a first mixture; S2: Add the polymerization solvent and the first mixture in S1 to the reactor to form a second mixture, then add the co-catalyst to the reactor, and charge the reactor with ethylene until the pressure inside the reactor reaches the predetermined polymerization pressure, then raise the temperature and stabilize it at the predetermined polymerization temperature; S3: Inject the catalyst into the reactor of S2 and maintain the pressure inside the reactor at the predetermined polymerization pressure. After reacting for 10-15 minutes, discharge the material, collect the polyethylene elastomer, dry it, and weigh it.

[0037] Specifically, the preparation of polyethylene elastomers is based on the coordination copolymerization reaction of ethylene and α-olefins catalyzed by a single active center catalyst. By controlling the type and content of comonomers, the distribution of short branches and crystallization behavior on the polymer chain can be controlled, thereby forming a microstructure in which amorphous and microcrystalline regions are separated. In this structure, the microcrystalline region, as a physical crosslinking point, endows the material with excellent elasticity and mechanical properties at room temperature, while the thermoplasticity of the molecular chain is retained, giving it good processability.

[0038] In one embodiment of this disclosure, the catalyst is one or more of a metallocene catalyst, a post-transition metal catalyst, and a non-metallocene catalyst, and the central metal element of the catalyst is selected from Ti, Zr, Hf, Cr, Fe, Co, and Ni.

[0039] Specifically, metallocene catalysts, post-transition metal catalysts, and non-metallocene catalysts all belong to single-active-site catalysts. They can control the polymerization process at the molecular level, enabling efficient copolymerization of ethylene and α-olefins. Furthermore, different metal centers affect the catalyst's activity, copolymerization ability, molecular weight regulation, and thermal stability. By selecting appropriate metal elements, the distribution and crystallization behavior of short branches in the polymer chain can be controlled, thereby forming a microstructure with phase separation between amorphous and microcrystalline regions. This allows the material to exhibit excellent elasticity and mechanical properties at room temperature, relying on microcrystals as physical crosslinking points, while maintaining good thermoplastic processability.

[0040] In one embodiment of this disclosure, the co-catalyst is selected from one or more of methylaluminoxane, modified methylaluminoxane, tri(pentafluorophenyl)borane, borate, triethylaluminum, triisobutylaluminum, and trihexylaluminum.

[0041] Specifically, the main function of these cocatalysts is to activate catalysts with Ti, Zr, Hf, Cr, Fe, Co, and Ni as the central metal elements, and generate highly active cationic centers through alkylation and / or anion abstraction, thereby initiating and maintaining the copolymerization reaction of ethylene and α-olefins.

[0042] In one embodiment of this disclosure, the polymerization solvent is selected from one or more of n-hexane, cyclohexane, n-heptane, 2-methylhexane, 3-methylhexane, isoalkanes Isopar C, and isoalkanes Isopar E. These solvents are all inert alkane compounds with good chemical stability and will not react with the catalyst or polymer. At the same time, these polymerization solvents can dissolve the generated polymer, maintain the fluidity of the system, and facilitate subsequent separation and processing.

[0043] In one embodiment of this disclosure, the predetermined polymerization temperature is 100-180°C. Within this temperature range, the polymerization system remains in a solution state, which is conducive to the full dissolution and uniform participation of ethylene and α-olefin monomers in the reaction. The predetermined polymerization pressure is 2.0-5.0 MPa, and the weight ratio of the first olefin and the second olefin in the first mixture is 0.5-3.0. The predetermined polymerization pressure is mainly determined by the partial pressure of ethylene. The pressure range of 2.0-5.0 MPa can maintain a high ethylene concentration, ensure sufficient polymerization rate and molecular weight, and promote the effective copolymerization of comonomers.

[0044] This disclosure also provides an application of a polyethylene elastomer in modified polyethylene, polypropylene, and engineering plastics. When the polyethylene elastomer provided in this disclosure is applied to modified general-purpose polyethylene and polypropylene, it can significantly improve the impact strength of the modified polyethylene and polypropylene samples, exhibiting high toughness, thus meeting the requirements of film applications for high puncture resistance.

[0045] This disclosure also provides an application of polyethylene elastomer in the preparation of optical films. When the polyethylene elastomer provided in this disclosure is extruded, blended with general-purpose polypropylene, silicone powder, light stabilizer, white oil, and antioxidant additives, and then blow-molded, the resulting film product can have the characteristics of high light transmittance, high haze, high toughness, and good light diffusion.

[0046] The embodiments of the present invention will be described in detail below with reference to the examples. All of the following embodiments employ... Figure 1 The preparation method shown is illustrated, but those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the examples were performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0047] The following methods were used to test the structure or properties of the ethylene and α-olefin copolymers produced in the examples described: High-temperature gel permeation chromatography (GPC) is used to test the weight-average molecular weight and molecular weight distribution of copolymers.

[0048] Gradient density meters are used to test the density of copolymers.

[0049] A melt indexer is used to test the melt index of copolymers.

[0050] Nuclear magnetic resonance (NMR) spectrometers are used to test the α-olefin insertion rate in copolymers.

[0051] Differential scanning calorimetry (DSC) is used to test the melting point of copolymers.

[0052] A haze meter is used to test the transmittance and haze of copolymers.

[0053] The drop impact strength tester is used to test the drop impact strength of copolymers.

[0054] A universal testing machine is used to test the tensile strength of polyolefins.

[0055] Impact testing machines are used to test the impact strength of polyolefins.

[0056] Integrating sphere transmission / reflection measurement systems are used to test the light diffusion properties of thin films.

[0057] Experimental Example 1 1.65 kg of n-hexane solvent, 0.42 kg of comonomer (1-heptene and 1-octene in a weight ratio of 0.9:1), 4 mmol of methylaluminoxane cocatalyst, and 7 µmol of tris(pentafluorophenyl)borane were added sequentially to a 5 L reactor. Ethylene was then introduced until the reactor pressure reached 3.2 MPa. The temperature was raised and stabilized at 135 °C. Finally, 6.2 µmol of metallocene catalyst (CAS 135072-61-6) was injected while maintaining the reactor pressure at 3.2 MPa. After reacting for 15 min, the product was discharged, copolymer A was collected, dried, and weighed. The physical properties of copolymer A are shown in Table 1.

[0058] Modified polyethylene was obtained by blending and extruding 1 part by weight of copolymer A with 9 parts by weight of polyethylene (grade GC 7260) and then injection molding. Modified polypropylene was obtained by blending and extruding 1 part by weight of copolymer A with 9 parts by weight of polypropylene (grade HA104E) and then injection molding. The mechanical properties of modified polyethylene and modified polypropylene are shown in Table 2.

[0059] One part by weight of copolymer A, two parts by weight of polypropylene resin, 0.015 parts by weight of silicone powder, 0.01 parts by weight of light stabilizer, 0.01 parts by weight of white oil and 0.01 parts by weight of antioxidant are blended and extruded in a twin-screw extruder and then granulated to obtain mixed granules. The mixed granules are blow molded to obtain film products. The properties of the film products are shown in Table 3.

[0060] Experiment Example 2 1.65 kg of n-hexane solvent, 0.78 kg of comonomer (1-heptene and 1-octene in a weight ratio of 0.9:1), 4 mmol of methylaluminoxane cocatalyst, and 7.7 µmol of tris(pentafluorophenyl)borane were added sequentially to a 5 L reactor. Ethylene was then introduced until the reactor pressure reached 3.5 MPa. The temperature was raised and stabilized at 155 °C. Finally, 7 µmol of metallocene catalyst (CAS135072-61-6) was injected while maintaining the reactor pressure at 3.5 MPa. After reacting for 10 min, the product was discharged, copolymer B was collected, dried, and weighed. The physical properties of copolymer B are shown in Table 1.

[0061] Modified polyethylene was obtained by blending and extruding 1 part by weight of copolymer B with 9 parts by weight of polyethylene (grade GC 7260) and then injection molding. Modified polypropylene was obtained by blending and extruding 1 part by weight of copolymer B with 9 parts by weight of polypropylene (grade HA104E) and then injection molding. The mechanical properties of modified polyethylene and modified polypropylene are shown in Table 2.

[0062] One part by weight of copolymer B, two parts by weight of polypropylene resin, 0.015 parts by weight of silicone powder, 0.01 parts by weight of light stabilizer, 0.01 parts by weight of white oil and 0.01 parts by weight of antioxidant were blended and extruded using a twin-screw extruder and then granulated to obtain mixed granules. The mixed granules were blow-molded to obtain film products. The properties of the film products are shown in Table 3.

[0063] Experimental Example 3 1.65 kg of n-hexane solvent, 1.2 kg of comonomer (1-heptene and 1-octene in a weight ratio of 0.9:1), 4 mmol of methylaluminoxane cocatalyst, and 7.7 µmol of tris(pentafluorophenyl)borane were added sequentially to a 5 L reactor. Ethylene was then introduced until the reactor pressure reached 3.9 MPa. The temperature was raised and stabilized at 125 °C. Finally, 7 µmol of metallocene catalyst (CAS135072-61-6) was injected while maintaining the reactor pressure at 3.9 MPa. After reacting for 15 min, the product was discharged, copolymer C was collected, dried, and weighed. The physical properties of copolymer C are shown in Table 1.

[0064] Modified polyethylene was obtained by blending and extruding 1 part by weight of copolymer C with 9 parts by weight of polyethylene (grade GC 7260) and then injection molding. Modified polypropylene was obtained by blending and extruding 1 part by weight of copolymer C with 9 parts by weight of polypropylene (grade HA104E) and then injection molding. The mechanical properties of modified polyethylene and modified polypropylene are shown in Table 2.

[0065] One part by weight of copolymer C, two parts by weight of polypropylene resin, 0.015 parts by weight of silicone powder, 0.01 parts by weight of light stabilizer, 0.01 parts by weight of white oil and 0.01 parts by weight of antioxidant are blended and extruded in a twin-screw extruder and then granulated to obtain mixed granules. The mixed granules are blow molded to obtain film products. The properties of the film products are shown in Table 3.

[0066] Experiment Example 4 1.65 kg of n-hexane solvent, 0.70 kg of comonomer (1-pentene and 1-hexene in a weight ratio of 0.6:1), and 4 mmol of modified methylaluminoxane cocatalyst were added sequentially to a 5 L reactor. Ethylene was then introduced until the reactor pressure reached 2.9 MPa. The temperature was raised and stabilized at 140 °C. Finally, 7 µmol of metallocene catalyst (CAS 132510-07-7) was injected while maintaining the reactor pressure at 2.9 MPa. After reacting for 15 min, the product was discharged, copolymer D was collected, dried, and weighed. The physical properties of copolymer D are shown in Table 1.

[0067] Modified polyethylene was obtained by blending and extruding 1 part by weight of copolymer D with 9 parts by weight of polyethylene (grade GC 7260) and then injection molding. Modified polypropylene was obtained by blending and extruding 1 part by weight of copolymer D with 9 parts by weight of polypropylene (grade HA104E) and then injection molding. The mechanical properties of modified polyethylene and modified polypropylene are shown in Table 2.

[0068] One part by weight of copolymer D, two parts by weight of polypropylene resin, 0.015 parts by weight of silicone powder, 0.01 parts by weight of light stabilizer, 0.01 parts by weight of white oil and 0.01 parts by weight of antioxidant were blended and extruded in a twin-screw extruder and then granulated to obtain mixed granules. The mixed granules were blow molded to obtain film products. The properties of the film products are shown in Table 3.

[0069] Example 5 1.65 kg of n-hexane solvent, 0.73 kg of comonomer (1-pentene and 1-hexene in a weight ratio of 0.6:1), and 4 mmol of modified methylaluminoxane cocatalyst were added sequentially to a 5 L reactor. Ethylene was then introduced until the reactor pressure reached 3.0 MPa. The temperature was raised and stabilized at 150 °C. Finally, 7 µmol of metallocene catalyst (CAS 132510-07-7) was injected while maintaining the reactor pressure at 3.0 MPa. After reacting for 10 min, the product was discharged, copolymer E was collected, dried, and weighed. The physical properties of copolymer E are shown in Table 1.

[0070] Modified polyethylene was obtained by blending and extruding 1 part by weight of copolymer E with 9 parts by weight of polyethylene (grade GC 7260) and then injection molding. Modified polypropylene was obtained by blending and extruding 1 part by weight of copolymer E with 9 parts by weight of polypropylene (grade HA104E) and then injection molding. The mechanical properties of modified polyethylene and modified polypropylene are shown in Table 2.

[0071] One part by weight of copolymer E, two parts by weight of polypropylene resin, 0.015 parts by weight of silicone powder, 0.01 parts by weight of light stabilizer, 0.01 parts by weight of white oil and 0.01 parts by weight of antioxidant were blended and extruded using a twin-screw extruder and then granulated to obtain mixed granules. The mixed granules were blow-molded to obtain film products. The properties of the film products are shown in Table 3.

[0072] Comparative Example 1 1.65 kg of n-hexane solvent, 0.79 kg of 1-octene, 5 mmol of methylaluminoxane co-catalyst, and 9 µmol of tris(pentafluorophenyl)borane were added sequentially to a 5 L reactor. Ethylene was then introduced until the reactor pressure reached 3.2 MPa. The temperature was raised and stabilized at 135 °C. Finally, 8 µmol of metallocene catalyst (CAS 135072-61-6) was injected while maintaining the reactor pressure at 3.2 MPa. After reacting for 15 min, the product was discharged, copolymer F was collected, dried, and weighed. The physical properties of copolymer F are shown in Table 1.

[0073] Modified polyethylene was obtained by blending and extruding 1 part by weight of copolymer F with 9 parts by weight of polyethylene (grade GC 7260) and then injection molding. Modified polypropylene was obtained by blending and extruding 1 part by weight of copolymer F with 9 parts by weight of polypropylene (grade HA104E) and then injection molding. The mechanical properties of modified polyethylene and modified polypropylene are shown in Table 2.

[0074] One part by weight of copolymer F, two parts by weight of polypropylene resin, 0.015 parts by weight of silicone powder, 0.01 parts by weight of light stabilizer, 0.01 parts by weight of white oil and 0.01 parts by weight of antioxidant are blended and extruded in a twin-screw extruder and then granulated to obtain mixed granules. The mixed granules are blow molded to obtain film products. The properties of the film products are shown in Table 3.

[0075] Comparative Example 2 1.65 kg of n-hexane solvent, 0.75 kg of comonomer 1-hexene, and 4 mmol of modified methylaluminoxane cocatalyst were added sequentially to a 5 L reactor. Ethylene was then introduced until the reactor pressure reached 3.0 MPa. The temperature was raised and stabilized at 150 °C. Finally, 7 µmol of metallocene catalyst (CAS 132510-07-7) was injected while maintaining the reactor pressure at 3.0 MPa. After reacting for 10 min, the product was discharged, copolymer G was collected, dried, and weighed. The physical properties of copolymer G are shown in Table 1.

[0076] Modified polyethylene was obtained by blending and extruding 1 part by weight of copolymer G with 9 parts by weight of polyethylene (grade GC 7260) and then injection molding. Modified polypropylene was obtained by blending and extruding 1 part by weight of copolymer G with 9 parts by weight of polypropylene (grade HA104E) and then injection molding. The mechanical properties of modified polyethylene and modified polypropylene are shown in Table 2.

[0077] One part by weight of copolymer G, two parts by weight of polypropylene resin, 0.015 parts by weight of silicone powder, 0.01 parts by weight of light stabilizer, 0.01 parts by weight of white oil and 0.01 parts by weight of antioxidant were blended and extruded in a twin-screw extruder and then granulated to obtain mixed granules. The mixed granules were blow molded to obtain film products. The properties of the film products are shown in Table 3.

[0078] Comparative Example 3 1.65 kg of n-hexane solvent, 0.73 kg of comonomers (0.21 kg of 1-pentene, 0.36 kg of 1-hexene, and 0.16 kg of 1-octene), and 4 mmol of modified methylaluminoxane cocatalyst were added sequentially to a 5 L reactor. Ethylene was then introduced until the reactor pressure reached 3.0 MPa. The temperature was raised and stabilized at 150 °C. Finally, 7 µmol of metallocene catalyst (CAS 132510-07-7) was injected while maintaining the reactor pressure at 3.0 MPa. After reacting for 10 min, the product was discharged, copolymer H was collected, dried, and weighed. The physical properties of copolymer H are shown in Table 1.

[0079] Modified polyethylene was obtained by blending and extruding 1 part by weight of copolymer H with 9 parts by weight of polyethylene (grade GC 7260) and then injection molding. Modified polypropylene was obtained by blending and extruding 1 part by weight of copolymer H with 9 parts by weight of polypropylene (grade HA104E) and then injection molding. The mechanical properties of modified polyethylene and modified polypropylene are shown in Table 2.

[0080] One part by weight of copolymer H, two parts by weight of polypropylene resin, 0.015 parts by weight of silicone powder, 0.01 parts by weight of light stabilizer, 0.01 parts by weight of white oil and 0.01 parts by weight of antioxidant are blended and extruded in a twin-screw extruder and then granulated to obtain mixed granules. The mixed granules are blow molded to obtain film products. The properties of the film products are shown in Table 3.

[0081] Table 1

[0082] As shown in Table 1, comparing copolymer AC and copolymer F, copolymer AC, with 1-heptene and 1-octene as mixed comonomers, exhibits both high transmittance and high haze. Its transmittance is >88.6%, and increases significantly with increasing amounts of mixed comonomers. Its haze is >18%, and decreases slowly with increasing amounts of mixed comonomers. Copolymer F, on the other hand, is a copolymer of ethylene and 1-octene. While it also has high transmittance (90.0%), its haze is low (6.1%). Therefore, copolymer F cannot simultaneously possess both high transmittance and high haze.

[0083] Similarly, as shown in Table 1, comparing copolymer DE and copolymer G, copolymer DE, with 1-pentene and 1-hexene as mixed comonomers, exhibits both high transmittance and high haze. Its transmittance is >90.7%, and increases significantly with increasing amounts of mixed comonomers. Its haze is >26.8%, and decreases slowly with increasing amounts of mixed comonomers. Copolymer G, a copolymer of ethylene and 1-hexene, also has high transmittance (90.2%), but low haze (10.3%). Therefore, copolymer G also struggles to combine high transmittance with high haze.

[0084] As can be seen from the characterization results in Table 1, comparing copolymer E and copolymer H, it can be found that copolymer H, which uses 1-pentene, 1-hexene and 1-octene as mixed olefin comonomers, has higher transmittance and lower haze, while copolymer E has both high transmittance and high haze. This is mainly because the microcrystal size in copolymer E is smaller and the defect density inside the microcrystal is higher, resulting in a larger interface area between the crystalline and amorphous regions, which enhances the scattering effect of light.

[0085] The polyethylene elastomer described in this disclosure is a copolymer of ethylene with a first olefin and a second olefin, wherein the comonomer is a mixed olefin composed of α-olefins with more than 4 carbon atoms and an odd number of carbon atoms, and α-olefins with more than 3 carbon atoms and an even number of carbon atoms. The experimental results show that when the total molar content of the first olefin and the second olefin in the copolymer is 3.0-10.0 mol%, the transmittance of the copolymer film can reach over 88.5%, and particularly, the haze is over 15%. When the content of the comonomer in the copolymer is 3.0-10.0 mol%, the density of the copolymer is 0.865-0.895 g / cm³. 3 This falls within the scope of polyethylene elastomers and polyethylene plasmons, and its haze should be below 10%. However, because this disclosure uses a mixture of odd-numbered and even-numbered carbon α-olefins as comonomers, the molecular chains of this copolymer are more prone to forming small and imperfect crystals during crystallization. This significantly increases the interfacial area (i.e., the total area of ​​scattering centers) between crystals and amorphous materials per unit volume. Furthermore, due to the diverse types of branches, the interface is no longer a smooth, clear boundary, but rather a diffuse, rough region with a more dramatic change in refractive index gradient. This complex interfacial structure has a much higher light scattering efficiency than a smooth interface. This enhances the scattering behavior between crystal planes, increasing its haze to >15%.

[0086] Furthermore, because the microcrystals are much smaller, the light transmittance does not decrease, so the film still exhibits high light transmittance.

[0087] Table 2

[0088] As shown in Table 2, compared with copolymer AC and copolymer F modified polyethylene, the impact strength of copolymer AC modified polyethylene, which uses 1-heptene and 1-octene as mixed comonomers, can be increased from 3.9 kJ / m. 2 Increased to 13.5 kJ / m 2 The above values ​​significantly exceed the impact strength of 11.9 kJ / m², which is far higher than that of the copolymer modified polyethylene of ethylene F and 1-octene. 2 Comparing polypropylene modified with copolymers AC and F, the impact strength of polypropylene modified with copolymer AC (using 1-heptene and 1-octene as mixed comonomers) can be increased from 19.9 kJ / m. 2 Increased to 36.2 kJ / m 2 The above values ​​significantly exceed the impact strength of 33.0 kJ / m², which is far higher than that of the copolymerized polypropylene modified with copolymers of ethylene (F) and 1-octene. 2 Therefore, copolymers using 1-heptene and 1-octene as mixed comonomers show better toughening effects when modifying general-purpose polyethylene and polypropylene.

[0089] Similarly, as shown in Table 2, compared with copolymers DE and G, the polyethylene modified with copolymer DE (using 1-pentene and 1-hexene as mixed comonomers) exhibits a higher impact strength, increasing from 3.9 kJ / m. 2 Increased to 9.9 kJ / m 2 The above values ​​significantly exceed the impact strength of 8.9 kJ / m², which is much higher than that of the copolymer modified polyethylene of copolymer G (ethylene) and 1-hexene. 2 Compared to copolymers DE and G, polypropylene modified with copolymer DE (using 1-pentene and 1-hexene as mixed comonomers) exhibits a higher impact strength, increasing it from 19.9 kJ / m. 2 Increased to 34.2 kJ / m 2 The above values ​​significantly exceed the impact strength of 30.5 kJ / m², which is far higher than that of the copolymer of ethylene and 1-hexene modified polypropylene. 2 Therefore, copolymers using 1-pentene and 1-hexene as mixed comonomers show better toughening effects on general-purpose polyethylene and polypropylene.

[0090] Table 3

[0091] As shown in Table 3, compared with the blown films obtained by mixing copolymer AC and copolymer F with polypropylene, silicone powder, light stabilizer, white oil, and antioxidant, the blown film with copolymer AC as the main raw material, using 1-heptene and 1-octene as mixed comonomers, exhibits a light transmittance of over 79.3%, a haze of over 95.0%, and a drop weight impact strength of over 635g, with excellent light diffusion performance. These are all significantly better than the blown film with copolymer F, using ethylene and 1-octene as the main raw material, which has a light transmittance of 75.8%, a haze of 82.5%, a drop weight impact strength of 560g, and poor light diffusion performance. Therefore, the blown film with copolymers of 1-heptene and 1-octene as the main raw material possesses the characteristics of high light transmittance, high haze, high toughness, and good light diffusion. Similarly, as shown in Table 3, comparing the blown films obtained from copolymers DE and G mixed with polypropylene, silicone powder, light stabilizers, white oil, and antioxidants, the blown film using copolymer DE (with 1-pentene and 1-hexene as mixed comonomers) as the main raw material exhibits a light transmittance of over 82.8%, a haze of over 95.1%, and a drop weight impact strength of over 605g, with excellent light diffusion performance. These are all significantly superior to the blown film using copolymer G (ethylene and 1-hexene as the main raw material), which has a light transmittance of 76.1%, a haze of 88.3%, a drop weight impact strength of 480g, and poor light diffusion performance. Therefore, the blown film using the copolymer with 1-pentene and 1-hexene as the main raw material possesses the characteristics of high light transmittance, high haze, high toughness, and good light diffusion.

[0092] The present disclosure provides a polyethylene elastomer, its preparation method, and its application. By copolymerizing ethylene with α-olefins having an odd number of carbon atoms (greater than 4) and α-olefins having an even number of carbon atoms (greater than 3), a polyethylene elastomer with both high light transmittance and high haze is obtained. This polyethylene elastomer can be used for the modification of polyethylene, polypropylene, and engineering plastics. The modified polyethylene and polypropylene samples show significantly improved impact strength and high toughness, thus meeting the requirements for high puncture resistance in film applications.

[0093] In addition, this polyethylene elastomer can also be used to prepare optical films. The resulting film products have the characteristics of high light transmittance, high haze, high toughness and good light diffusion, which can meet the requirements of polyethylene films in high-end application scenarios.

[0094] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein. The scope of the invention is defined by the appended claims.

Claims

1. A polyethylene elastomer, wherein the polyethylene elastomer is a copolymer of ethylene with a first olefin and a second olefin, characterized in that, The polyethylene elastomer has a light transmittance > 88.5% and a haze > 15%. The total molar content of the first olefin and the second olefin in the polyethylene elastomer is 3.0-10.0 mol%. The first olefin is an α-olefin with more than 4 carbon atoms and an odd number of carbon atoms, and the second olefin is an α-olefin with more than 3 carbon atoms and an even number of carbon atoms. The weight ratio of the first olefin and the second olefin in the polyethylene elastomer is 0.8-3.

0. After continuous self-nucleation annealing, the average lamellar thickness of the polyethylene elastomer is 2.0-3.6 nm, and it does not contain any portion with an average lamellar thickness greater than 4.0 nm.

2. The polyethylene elastomer according to claim 1, characterized in that, The first olefin is selected from one of 1-pentene, 1-heptene, 1-nonene, and 1-undecene.

3. The polyethylene elastomer according to claim 2, characterized in that, The second olefin is selected from one of 1-butene, 1-hexene, 1-octene, and 1-decene.

4. The polyethylene elastomer according to claim 3, characterized in that, The combination of the first olefin and the second olefin is one of 1-pentene / 1-butene, 1-pentene / 1-hexene, 1-pentene / 1-octene, 1-pentene / 1-decene, 1-heptene / 1-butene, 1-heptene / 1-hexene, 1-heptene / 1-octene, 1-heptene / 1-decene, 1-nonene / 1-butene, 1-nonene / 1-hexene, 1-nonene / 1-octene, and 1-nonene / 1-decene.

5. The polyethylene elastomer according to claim 1, characterized in that, The density of the polyethylene elastomer is 0.865-0.895 g / cm³. 3 The weight-average molecular weight is 50,000-270,000 g / mol, the molecular weight distribution is 1.5-6.0, the melting point is 50-100℃, and the melt index is 0.05-10.0 g / 10min.

6. A method for preparing a polyethylene elastomer according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1: The first olefin and the second olefin are mixed in a certain proportion to form a first mixture; S2: Add the polymerization solvent and the first mixture in S1 to the reactor to form a second mixture, then add the co-catalyst to the reactor, and charge the reactor with ethylene until the pressure inside the reactor reaches the predetermined polymerization pressure, then raise the temperature and stabilize it at the predetermined polymerization temperature; S3: Inject the catalyst into the reactor of S2 and maintain the pressure inside the reactor at the predetermined polymerization pressure. After reacting for 10-15 minutes, discharge the material, collect the polyethylene elastomer, dry it, and weigh it.

7. The preparation method according to claim 6, characterized in that, The catalyst is one or more of metallocene catalysts, post-transition metal catalysts, and non-metallocene catalysts, and the central metal element of the catalyst is selected from Ti, Zr, Hf, Cr, Fe, Co, and Ni.

8. The preparation method according to claim 6, characterized in that, The co-catalyst is selected from one or more of methylaluminoxane, modified methylaluminoxane, tris(pentafluorophenyl)borane, borate, triethylaluminum, triisobutylaluminum, and trihexylaluminum.

9. The preparation method according to claim 6, characterized in that, The polymerization solvent is selected from one or more of n-hexane, cyclohexane, n-heptane, 2-methylhexane, 3-methylhexane, isoalkanes Isopar C, and isoalkanes Isopar E.

10. The preparation method according to claim 6, characterized in that, The predetermined polymerization temperature is 100-180℃, the predetermined polymerization pressure is 2.0-5.0MPa, and the weight ratio of the first olefin and the second olefin in the first mixture is 0.5-3.

0.

11. The application of a polyethylene elastomer in modified polyethylene, polypropylene, and engineering plastics, characterized in that, The polyethylene elastomer is the polyethylene elastomer according to any one of claims 1 to 5.

12. An application of a polyethylene elastomer in the preparation of optical thin films, characterized in that, The polyethylene elastomer is the polyethylene elastomer according to any one of claims 1 to 5.

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