High light transmission ethylene copolymer and use thereof

Abstract

This invention discloses a high-transmittance ethylene copolymer and its applications. In this copolymer, the molar content of the second olefin X is 1.8-9.9 mol%, and the second olefin X is an olefin with more than 4 carbon atoms and an odd number of carbon atoms. The molar content of the [EXX] segment is 0.1-5.0 mol% of the total ternary segment content, the molar content of the [EEE] segment is 70-90 mol%, the molar content of the [EXE] segment is 2.0-8.0 mol%, the molar content of the [XEE] segment is 0.5-3.0 mol%, and the molar content of the [XEX] segment is 3.5-10.0 mol%. In this copolymer, when the molar content of the [EXX] segment reaches 0.15 mol%, the transmittance of the copolymer film after hot pressing is not less than 90%, exhibiting extremely high atom economy of the second olefin X. This copolymer can be applied in photovoltaic films, toughening of polyolefin materials, wire and cable, and modification of engineering plastics.

Description

Technical Field

[0001] This invention relates to a polyolefin material, and more specifically, to an ethylene copolymer with high light transmittance and its applications. Background Technology

[0002] High-transmittance polyolefin materials, such as polyethylene elastomer (POE), ethylene-vinyl acetate copolymer (EVA), cyclic olefin copolymer (COC), and polymethyl methacrylate (PMMA), are widely used in photovoltaic encapsulation, optical lenses, packaging materials, and medical devices. Taking POE as an example, its excellent anti-PID properties, high water vapor barrier properties, weather resistance, and high electrical insulation properties are gradually replacing EVA in the photovoltaic film field. However, POE is relatively expensive, resulting in high costs for POE photovoltaic films. This is mainly due to the high price of its comonomer α-olefin and the long and costly solution-based production process. Therefore, it is crucial to reduce the amount of α-olefin in POE while maintaining its high transmittance and lowering production costs.

[0003] In existing POE production, the α-olefin comonomers are all even-numbered carbons, mainly 1-butene, 1-hexene, and 1-octene. This is primarily because odd-numbered carbon α-olefins are expensive, and there is currently no low-cost supply of odd-numbered carbon α-olefins, making it difficult to meet the needs of large-scale commercial production. Currently, domestic coal chemical enterprises have made breakthroughs in coal-to-olefins production technology, enabling the production of high-quality coal-based α-olefins. Coal-based α-olefins contain olefins with different carbon numbers (C5-C16), making the efficient utilization of odd-numbered carbon olefins an urgent priority. CN1328581A proposes a polymer obtained from a first olefin having less than 4 carbon atoms and a second olefin having more than 5 and an odd number of carbon atoms. The molar ratio of the first olefin to the second olefin in the polymer ranges from 90:10 to 99.9:0.1. A method for preparing the polymer is also provided, employing a Ziegler-Natta catalyst or catalyst system, reacting the first and second olefins in one or more reaction zones at atmospheric pressure and 200 kg / cm². 2 Between ambient temperature and 300℃, the polymer density ranges from 0.910 to 0.950 g / cm³. 3The polymer density in this invention falls within the range of LLDPE, MDPE, and HDPE, excluding the density range of POE, and the catalyst used is a Ziegler-Natta catalyst. Furthermore, CN118271498A provides an optical POE material, its preparation method, and its applications. In the sequence structure of this optical POE material, the proportion of the ternary sequence EEE is less than 80%, the proportion of the EXE+XEX sequence is greater than 10%, and the molar insertion rate of the comonomer is 10%–20%. The optical POE material provided by this invention possesses both high light transmittance and a low melting point, making it highly suitable for applications in laser welding. The comonomer used in this invention is still an even-numbered carbon α-olefin, selected from one or more of butene, hexene, and octene.

[0004] Therefore, developing a POE material that combines high light transmittance and low comonomer insertion rate is extremely challenging and crucial for improving the added value and market competitiveness of POE products. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a high-transmittance ethylene copolymer and its applications. The copolymer provided by this invention has the dual advantages of low α-olefin insertion and high transmittance.

[0006] According to one objective of the present invention, a copolymer of ethylene and a second olefin is provided, wherein the second olefin X comprises 1.8-9.9 mol% of the copolymer, and the second olefin X is an olefin with more than 4 carbon atoms and an odd number of carbon atoms. The [EXX] fragment comprises 0.1-5.0 mol% of the total ternary fragment content in the copolymer. In the copolymer of the present invention, the ternary fragments are divided into six types: [EEE], [EXE], [XEE], [EXX], [XEX], and [XXX], where E represents an ethylene unit. In the present invention, the arrangement direction of the ternary fragments is not distinguished; therefore, the [EXX] fragment and the [XXE] fragment are considered the same fragment and are both represented by the [EXX] fragment; the [XEE] fragment and the [EEX] fragment are also considered the same fragment and are both represented by the [XEE] fragment. In the art, the content of each ternary fragment can be obtained by carbon NMR spectroscopy, which is a well-known method in the industry.

[0007] According to a preferred embodiment of the present invention, in the copolymer, the molar content of the [EEE] fragment accounts for 70-90 mol% of the total ternary fragment content, the molar content of the [EXE] fragment accounts for 2.0-8.0 mol% of the total ternary fragment content, the molar content of the [XEE] fragment accounts for 0.5-3.0 mol% of the total ternary fragment content, and the molar content of the [XEX] fragment accounts for 3.5-10.0 mol% of the total ternary fragment content.

[0008] According to a preferred embodiment of the present invention, in the copolymer, the second olefin X is selected from one or more of 1-pentene, 1-heptene, 1-nonene, and 1-undecene.

[0009] According to a preferred embodiment of the present invention, the copolymer has a weight-average molecular weight of 50,000-300,000 g / mol, a molecular weight distribution of 1.5-8.0, a melting point of 60-100℃, and a density of 0.868-0.898 g / cm³. 3 The tensile strength is 5-50 MPa.

[0010] The present invention also provides a method for preparing the above-mentioned copolymer, wherein the copolymer is prepared by solution polymerization, and the catalyst used for polymerization is a metallocene catalyst, wherein the central metal element M of the metallocene catalyst is bonded to N, C and Cl atoms, and the bite angle of the central metal element M is 105-115°. The polymerization temperature is 100-180℃, and the polymerization pressure is 1.8-5.0 MPa.

[0011] The polymerization solution is selected from one or more of n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, 2-methylhexane, 3-methylhexane, isoalkanes Isopar C, and isoalkanes Isopar E.

[0012] The metallocene catalyst is selected from one or more of bridged metallocene catalysts, non-bridged metallocene catalysts, and restricted geometry catalysts, and the co-catalyst is selected from one or more of methylaluminoxane, modified methylaluminoxane, tri(pentafluorophenyl)borane, borate, triethylaluminum, triisobutylaluminum, and trihexylaluminum.

[0013] Preferably, when the molar content of the [EXX] fragment in the copolymer reaches 0.15 mol% of the total ternary fragment content, the light transmittance of the copolymer film after hot pressing is not less than 90%, preferably not less than 90.5%.

[0014] The present invention also provides an application of the above copolymer, which can be used to prepare photovoltaic films, toughening agents for polyolefin materials, wires and cables, and engineering plastic modifiers, and has a wide range of applications.

[0015] The present invention has the following outstanding gain effects:

[0016] (1) In the copolymer described in this invention, the second olefin X is an α-olefin with more than 4 carbon atoms and an odd number of carbons (preferably one or more of 1-pentene, 1-heptene, 1-nonene, and 1-undecene). During the crystallization process of the copolymer molecular chain, the branched structure of odd-numbered carbons is less prone to crystallization behavior, and compared with the branched structure of even-numbered carbons, the crystallinity of the α-olefin copolymer of odd-numbered carbons is lower. As is well known, the transmittance of a copolymer is closely related to the content of amorphous regions. The higher the content of amorphous regions, the higher the transmittance. Therefore, the ethylene copolymer with an odd-numbered carbon branched structure has a higher transmittance than the ethylene copolymer with an even-numbered carbon branched structure.

[0017] (2) Experimental studies have shown that when the insertion rate of the second olefin X in the copolymer of the present invention reaches 2.5 mol%, the resulting copolymer of ethylene and odd-numbered carbon α-olefins has extremely high light transmittance, greater than 90.5%, and a copolymer density of approximately 0.895 g / cm³. 3 Compared to lower-density copolymers of ethylene and 1-octene, such as Dow Chemical's Engage 8003 POE, which has a density of approximately 0.885 g / cm³, this is significantly lower. 3 The transmittance is only 89.0%, while Engage 8003 grade POE has a 1-octene insertion rate of over 20 wt%. Therefore, the ethylene and odd-carbon α-olefin copolymer described in this invention only requires an extremely low odd-carbon α-olefin insertion rate to achieve the required high transmittance, exhibiting extremely high α-olefin atom economy. Since the price of α-olefins is much higher than that of ethylene, this significantly enhances the market competitiveness of the ethylene and odd-carbon α-olefin copolymer. For example, when the molar content of the copolymer [EXX] fragment reaches 0.15 mol% of the total ternary fragment content, the transmittance of the copolymer film after hot pressing is not less than 90%.

[0018] (3) Because the odd-carbon α-olefin insertion rate is required to be low in the ethylene and odd-carbon α-olefin copolymer described in this invention, it has a higher melting point and tensile strength. A higher melting point improves the processing performance when this copolymer is used to toughen and modify general-purpose or engineering plastics. Higher tensile strength improves the tensile strength and application range of the modified material after modification of general-purpose or engineering plastics. Therefore, this ethylene and odd-carbon α-olefin copolymer is not only suitable for photovoltaic films and medical packaging, which require high light transmittance, but also for plastic modification and toughening, which require high mechanical properties. Attached Figure Description

[0019] Figure 1 This is the carbon NMR spectrum of ethylene and odd-carbon α-olefin copolymer A (Example 1).

[0020] Figure 2 This is a stress-strain curve of an ethylene-α-olefin copolymer. Detailed Implementation

[0021] The embodiments of the present invention will be described in detail below with reference to examples. However, 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 in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0022] The following methods were used to test the structure or properties of the ethylene and α-olefin copolymers produced in the examples described:

[0023] High-temperature gel permeation chromatography (GPC) is used to test the weight-average molecular weight and molecular weight distribution of copolymers.

[0024] Gradient density meters are used to test the density of copolymers.

[0025] Nuclear magnetic resonance (NMR) spectrometers are used to test the α-olefin insertion rate in copolymers.

[0026] A universal testing machine is used to test the tensile strength of copolymers.

[0027] Differential scanning calorimetry (DSC) is used to test the melting point and enthalpy of copolymers.

[0028] A haze meter is used to test the light transmittance of copolymers.

[0029] Example 1

[0030] In a 10L reactor that has been dehydrated and deoxygenated, 5L of n-hexane solvent, 1.4L of the second olefin 1-heptene, 10mmol of methylaluminoxane co-catalyst, and 18μmol of tris(pentafluorophenyl)borane were added sequentially. Ethylene was then introduced until the reactor pressure reached 3MPa. The temperature was raised and stabilized at 130℃. Finally, 16μmol of metallocene CGC catalyst (CAS135072-61-6) was injected while maintaining the reactor pressure at 3MPa. After reacting for 10 minutes, the product was discharged, copolymer A was collected, dried, and weighed. The physical properties of copolymer A are shown in Table 1, and the carbon NMR spectroscopy results are shown in Table 2.

[0031] Example 2

[0032] In a 10L reactor that has been dehydrated and deoxygenated, 5.5L of cyclohexane solvent, 2.0L of the second olefin 1-heptene, and 8mmol of modified methylaluminoxane co-catalyst were added sequentially. Ethylene was then introduced until the reactor pressure reached 3MPa. The temperature was raised and stabilized at 150℃. Finally, 14μmol of metallocene catalyst (CAS132510-07-7) was injected while maintaining the reactor pressure at 3MPa. After reacting for 10 minutes, the product was discharged, copolymer B was collected, dried, and weighed. The physical properties of copolymer B are shown in Table 1, and the carbon NMR spectroscopy results are shown in Table 2.

[0033] Example 3

[0034] In a 10L reactor that has been dehydrated and deoxygenated, 6L of isoparaffin Isopar E solvent, 2.5L of the second olefin 1-heptene, and 8mmol of modified methylaluminoxane co-catalyst were added sequentially. Ethylene was then introduced until the reactor pressure reached 4MPa. The temperature was raised and stabilized at 120℃. Finally, 15μmol of metallocene catalyst (CAS100163-29-9) was injected while maintaining the reactor pressure at 4MPa. After reacting for 10 minutes, the product was discharged, copolymer C was collected, dried, and weighed. The physical properties of copolymer C are shown in Table 1, and the carbon NMR spectroscopy results are shown in Table 2.

[0035] Example 4

[0036] In a 10L reactor that has been dehydrated and deoxygenated, 5L of n-hexane solvent, 1.0L of the second olefin 1-heptene, 0.8L of the second olefin 1-pentene, 1mmol of triisobutylaluminum co-catalyst, and 18μmol of tris(pentafluorophenyl)borane were added sequentially. Ethylene was then introduced until the reactor pressure reached 3MPa. The temperature was raised and stabilized at 140℃. Finally, 15μmol of metallocene catalyst (CAS135072-61-6) was injected while maintaining the reactor pressure at 3MPa. After reacting for 10 minutes, the product was discharged, copolymer D was collected, dried, and weighed. The physical properties of copolymer D are shown in Table 1, and the carbon NMR spectroscopy results are shown in Table 2.

[0037] Comparative Example 1

[0038] In a 10L reactor that has been dehydrated and deoxygenated, 5L of n-hexane solvent, 1.4L of 1-octene, 10mmol of methylaluminoxane co-catalyst, and 18μmol of tris(pentafluorophenyl)borane were added sequentially. Ethylene was then introduced until the reactor pressure reached 3MPa. The temperature was raised and stabilized at 130℃. Finally, 16μmol of metallocene CGC catalyst (CAS 135072-61-6) was injected while maintaining the reactor pressure at 3MPa. After reacting for 10 minutes, the product was discharged, copolymer E was collected, dried, and weighed. The physical properties of copolymer E are shown in Table 1, and the carbon NMR spectroscopy results are shown in Table 2.

[0039] Comparative Example 2

[0040] In a 10L reactor that has been dehydrated and deoxygenated, 5L of n-hexane solvent, 1.4L of the second olefin 1-heptene, and 30mmol of triethylaluminum co-catalyst were added sequentially. Ethylene was then introduced until the reactor pressure reached 3MPa. The temperature was raised and stabilized at 105℃. Finally, 1g of supported Ziegler-Natta catalyst A (prepared according to the method described below) was added, and the reactor pressure was maintained at 3MPa. After reacting for 10 minutes, the product was discharged, copolymer F was collected, dried, and weighed. The physical properties of copolymer F are shown in Table 1, and the carbon NMR spectroscopy results are shown in Table 2.

[0041] The preparation method of the supported Ziegler-Natta catalyst A is as follows, which is the same as the preparation method of catalyst A in Example 1 of comparative patent CN1328581A:

[0042] In a 250 mL flask equipped with a reflux condenser and a stirrer, 2 g of magnesium chloride with a total water content of 1.5% (w / w) was suspended in 60 mL of highly purified hexane. A 1:1 molar mixture of 4 mL of dipentyl ether and ethanol was added to the flask, and the mixture was stirred under reflux for 3 hours. The mixture was cooled to ambient temperature, and 10 g of triethylaluminum was added dropwise to avoid excessive heat of formation. The resulting slurry was cooled to room temperature under stirring, and then washed 12 times with 50 mL of hexane each time to obtain a slurry containing the activated carrier.

[0043] Add 2 mL of a 1:1 molar mixture of ethanol and 1-nonanol to the slurry containing the activated carrier, and stir the slurry at ambient temperature for 3 hours. Then add 15 mL of TiCl4, and stir the mixture under reflux for 2 hours. After cooling, wash the slurry 10 times with 50 mL of hexane each time, and then dry it.

[0044] Comparative Example 3

[0045] In a 10L reactor that has been dehydrated and deoxygenated, 5L of n-hexane solvent, 1.0L of the second olefin 1-heptene, 0.8L of the second olefin 1-pentene, and 30mmol of triethylaluminum co-catalyst were added sequentially. Ethylene was then introduced until the reactor pressure reached 12MPa. The temperature was raised and stabilized at 230℃. Finally, 1g of Ziegler-Natta catalyst B (in which titanium tetrachloride and vanadium oxychloride were mixed in a 2:8 ratio) was added, and the reactor pressure was maintained at 12MPa. After reacting for 10 minutes, the product was discharged, copolymer G was collected, dried, and weighed. The physical properties of copolymer G are shown in Table 1, and the carbon NMR spectroscopy results are shown in Table 2.

[0046] Comparative Example 4

[0047] In a 10L dehydrated and deoxygenated reactor, 5L of n-hexane solvent, 2.0L of the second olefin 1-heptene, and 10mmol of methylaluminoxane co-catalyst were added sequentially. Ethylene was then introduced until the reactor pressure reached 3MPa. The temperature was raised and stabilized at 130℃. Finally, 16μmol of the metallocene catalyst diazotectic dichlorotitanium (CAS1271-19-8) was injected while maintaining the reactor pressure at 3MPa. After reacting for 10 minutes, the product was discharged, copolymer H was collected, dried, and weighed. The physical properties of copolymer H are shown in Table 1, and the carbon NMR spectroscopy results are shown in Table 2. In the diazotectic dichlorotitanium (CAS 1271-19-8) molecule, the bond angle between the titanium atom and the cyclopentadienyl ligand is close to 120°.

[0048] Table 1 Characterization results of copolymer AH

[0049]

[0050] Table 2. CMR characterization results of copolymer AH

[0051]

[0052] As shown in Tables 1 and 2, under the same polymerization conditions, copolymer A has a lower melting point and lower enthalpy of fusion than copolymer E, indicating that the branched structure with an odd number of carbon atoms is less prone to crystallization. Copolymer A has a high light transmittance of 90.7%, higher than the 89.6% of copolymer E. According to... Figure 1 The NMR spectroscopy results show that the insertion rate of 1-heptene in copolymer A is only 3.51 mol%, approximately 11.31 wt% by weight, while the insertion rate of 1-octene in copolymer E is 3.68 mol%, approximately 13.28 wt% by weight. This demonstrates that using odd-numbered carbon 1-heptene as a comonomer offers higher atom economy in POE production. Furthermore, copolymer A exhibits a tensile strength of 26.8 MPa, significantly higher than the 18.9 MPa of copolymer E (see...). Figure 2 ).

[0053] Copolymers F and G were prepared using supported and unsupported Ziegler-Natta catalysts. The second olefin X insertion rate of copolymer F was 1.11 mol%, with a [EXX] fragment content of 0.47 mol%, but the [EXE] and [XEX] fragment contents were only 0.90 mol% and 0.02 mol%, respectively. Therefore, the [EEE] fragment content in copolymer F was as high as 96.42 mol%, resulting in a transmittance of only 32.6%. Due to the multi-active-center characteristics of the supported Ziegler-Natta catalyst, even increasing the content of the second olefin X in the polymerization system did not significantly improve the second olefin X insertion rate. Copolymer G was prepared at 230 °C and 12 MPa (i.e., Sclairtech solution polymerization process). Under the process conditions of Comparative Example 3, copolymer G had a second olefin X insertion rate of 1.77 mol%, with a [EXX] fragment content of 0.51 mol%, but the [EXE] and [XEX] fragment contents were only 1.52 mol% and 0.04 mol%, respectively. Therefore, the [EEE] fragment content in copolymer G is as high as 94.09 mol%, resulting in a light transmittance of only 35.1%. Because this production process uses an unsupported Ziegler-Natta catalyst, even increasing the amount of the second olefin X cannot yield a density lower than 0.918 g / cm³. 3The copolymer. Therefore, neither supported nor unsupported Ziegler-Natta catalysts can produce high-transmittance ethylene copolymers with ternary sequence fragment content within the range described in this invention patent.

[0054] Copolymer H was prepared using solution polymerization with a catalyst of diazocarboxytimonochromocene (CAS1271-19-8). The bond angle between the titanium atom and the cyclopentadienyl ligand in this metallocene catalyst molecule is close to 120°, significantly higher than the 105-115° central metal bite angle of the restricted geometry CGC metallocene catalyst used in Examples 1-4. Therefore, the contents of [EXE], [EXX], [XEX], [XEE], and [EEE] fragments in copolymer H are 4.29 mol%, 0.08 mol%, 1.57 mol%, 10.60 mol%, and 83.46 mol%, respectively. The second olefin X is concentrated in the [XEE] fragment, which is much higher than the [XEE] fragment content in Examples 1-4. The [XEX] fragment content is low, and the [EXX] fragment content is only 0.08 mol%, resulting in a transmittance of only 80.1% for copolymer H. The large central metal bite angle of the titanium dichlorodicyclopentadiene catalyst resulted in low content of [EXX] and [XEX] fragments, which severely affected the transmittance of the copolymer.

[0055] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A copolymer of ethylene and a second olefin, characterized in that, The copolymer contains 1.8-9.9 mol% of the second olefin X, which is an olefin with more than 4 carbon atoms and an odd number of carbon atoms. The copolymer contains 0.1-5.0 mol% of the total ternary fragment content. The ternary fragments are divided into six types: [EEE], [EXE], [XEE], [EXX], [XEX], and [XXX], where E represents an ethylene unit. The copolymer is prepared by solution polymerization, and the catalyst used for polymerization is a metallocene catalyst. The central metal element M of the metallocene catalyst is bonded to N, C, and Cl atoms, and the bite angle of the central metal element M is 105-115°. The [EEE] fragment accounts for 70-90 mol% of the total ternary fragment content, the [EXE] fragment accounts for 2.0-8.0 mol% of the total ternary fragment content, the [XEE] fragment accounts for 0.5-3.0 mol% of the total ternary fragment content, and the [XEX] fragment accounts for 3.5-10.0 mol% of the total ternary fragment content. The metallocene catalyst is selected from one or more of the following: bridged metallocene catalysts, non-bridged metallocene catalysts, and restricted geometry catalysts; the co-catalyst is selected from one or more of the following: methylaluminoxane, modified methylaluminoxane, tri(pentafluorophenyl)borane, borate, triethylaluminum, triisobutylaluminum, and trihexylaluminum.

2. The copolymer according to claim 1, characterized in that, The second olefin X is selected from one or more of 1-pentene, 1-heptene, 1-nonene, and 1-undecene.

3. The copolymer according to claim 1, characterized in that, The copolymer has a weight-average molecular weight of 50,000-300,000 g / mol, a molecular weight distribution of 1.5-8.0, a melting point of 60-100 °C, and a density of 0.868-0.898 g / cm³. 3 The tensile strength is 5-50 MPa.

4. The copolymer according to claim 1, characterized in that, The polymerization temperature is 100-180 ℃, the polymerization pressure is 1.8-5.0 MPa, and the mass of the second olefin X in the solution accounts for 12.0-40.0 wt% of the total mass of the solution.

5. The copolymer according to claim 1, characterized in that, The polymerization solution is selected from one or more of n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, 2-methylhexane, 3-methylhexane, isoparaffin Isopar C, and isoparaffin Isopar E.

6. The use of the copolymer according to any one of claims 1-5 in the preparation of photovoltaic films, toughening agents for polyolefin materials, wire and cable modifiers, or engineering plastic modifiers.

7. The application according to claim 6, characterized in that, When the molar content of the copolymer [EXX] fragment accounts for 0.15 mol% of the total ternary fragment content, the light transmittance of the copolymer film after hot pressing is not less than 90%.

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