A propylene / alpha-olefin copolymer, a method for preparing the same, and use thereof

Abstract

The invention relates to a propylene / ethylene or propylene / alpha-olefin copolymer having the following characteristics: (a) molecular weight Mw: 2.0 x 10 4 g / mol to 40.0 x 10 4 g / mol; (b) density: 0.860 to 0.890 g / cm 3 ; (c) molecular weight distribution Mw / Mn: 2.0 to 4.0; (d) ∑ΔH T ≤ 4 J / g measured using a differential scanning calorimeter continuously self-nucleated / annealing (SSA), wherein T denotes the melting peak temperature of the segmented melting range measured by SSA, 85 °C ≤ T ≤ 120 °C; and ∑ΔH T / ΔH 总 ≥ 90%. The propylene-based copolymer based on the invention as an additive for the CPP cast film heat-sealing layer shows improved properties of the composite film material tear strength and drop dart impact due to the defined ∑ΔH T .

Description

Technical Field

[0001] This invention relates to polyolefin elastomer materials, and more particularly to a copolymer of propylene / α-olefin, a method for its preparation, and its applications. Background Technology

[0002] Polypropylene (PP) is a type of polyolefin material, transparent and lightweight, possessing excellent chemical resistance, high-temperature resistance, electrical insulation, and abrasion resistance. It is widely used in film materials for food and pharmaceutical packaging, automotive parts, clothing, daily necessities, and fiber products. Based on production processes, common polypropylene packaging film materials can be divided into: extruded cast film, biaxially oriented film, and blown extrusion film. Among these, cast polypropylene film, or CPP cast film, is a large category. It is a non-stretched, non-oriented flat extruded film produced through melt casting and rapid cooling, characterized by good transparency, high gloss, good stiffness, good moisture barrier properties, and excellent heat resistance. The production process includes: feeding, batching and weighing, melt extrusion, thickness measurement, edge trimming, corona treatment, traction, winding, slitting, packaging, and warehousing.

[0003] Traditional CPP cast films, depending on their functionality, can have a layered structure of three or more layers: a heat-sealing layer, a core layer, and a corona layer. The core layer is typically made of homopolymer polypropylene, modified and toughened with various elastomers to reduce brittleness and provide the film with mechanical properties such as stiffness, tear resistance, tensile strength, and toughness. Appropriate mechanical properties ensure the outer packaging material's protective function for the packaged goods, preventing them from scattering or being damaged during transportation and transfer.

[0004] From the perspective of the blending modification mechanism, when an elastomer is added to homopolymer polypropylene for blending, a "sea-island" structure is formed in the microstructure, where the homopolymer polypropylene is the continuous phase and the elastomer is the dispersed phase. The continuous phase provides the material's modulus-related mechanical properties, while the introduction of the dispersed phase can reduce the crystallization of the continuous phase, improving elasticity and impact resistance. Generally speaking, the more uniform the particle size distribution and the smaller the particle size of the dispersed phase, the higher the toughening effect, especially under low-temperature conditions. Conversely, if the blending effect is poor, microphase separation will occur between the base material and the modified material, significantly reducing the toughening effect and affecting product performance. Modified materials with good compatibility also offer greater "flexibility" in blending formulation control, meaning that adding fewer parts can achieve the same toughening effect, reducing costs.

[0005] In view of this, how to optimize the tear resistance and drop impact resistance of polypropylene base materials and minimize costs through the adjustment of the composition and structure of modified materials has always been a hot research topic in this field. Summary of the Invention

[0006] To address the aforementioned problems, this invention improves the heat-sealing performance of the polyolefin film by adjusting the structure and composition of the polyolefin elastomer material, thereby simultaneously reducing the initial sealing temperature and widening the heat-sealing temperature range.

[0007] On the one hand, the present invention provides a copolymer of propylene / ethylene or propylene / α-olefin, said copolymer having the following characteristics:

[0008] (a) Molecular weight Mw: 2.0 × 10 4 g / mol~40.0×10 4 g / mol;

[0009] (b) Density: 0.860 to 0.890 g / cm³ 3 ;

[0010] (c) Molecular weight distribution Mw / Mn: 2.0 to 4.0;

[0011] (d) ∑ΔH measured continuously using differential scanning calorimetry (SSA) with self-nucleation / annealing (SSA) T ≤4J / g, where T represents the melting peak temperature of the segmented melting range measured by SSA, 85℃≤T≤120℃; and ∑ΔH T / ΔH 总 ≥90%.

[0012] Typically, the molecular weight of a polymer is influenced by a variety of factors. For example, the molecular weight can be controlled over a wide range by adjusting the temperature of the polymerization reaction. For a given polymerization temperature, the molecular weight of the copolymer can also be affected by adjusting the type and amount of monomers added. Furthermore, even with the same monomer ratio and polymerization temperature, different catalytic systems can produce polymers with vastly different molecular weights (Mw), ranging from several thousand to tens of thousands or even millions. Moreover, different molecular weights affect the processing properties of the polymer and the mechanical properties of the finished product. In this invention, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) are the molecular weights converted from polystyrene analyzed by gel permeation chromatography (GPC), and the molecular weight distribution can be calculated from the Mw / Mn ratio.

[0013] Preferably, the weight-average molecular weight range of the propylene / ethylene or propylene / α-olefin copolymer is 3 × 10⁻⁶. 4 g / mol ~ 35.0 × 10 4 g / mol; preferably, the weight-average molecular weight range of the propylene / ethylene or propylene / α-olefin copolymer is 3 × 10⁻⁶ g / mol. 4 g / mol ~ 30.0 × 10 4 g / mol;

[0014] Preferably, the molecular weight distribution range of the propylene / ethylene or propylene / α-olefin copolymer is 2.5 to 3.5.

[0015] It is also worth mentioning that the copolymer described in this invention is a copolymer of propylene / ethylene or propylene / α-olefin. It should be specifically noted that the vast majority of the constituent units in the polymer are derived from propylene.

[0016] Preferably, the propylene / ethylene or propylene / α-olefin copolymer contains 50% to 97% molar fraction of propylene-derived units and 3% to 50% molar fraction of ethylene or α-olefin-derived units.

[0017] Preferably, the propylene / ethylene or propylene / α-olefin copolymer contains 60% to 90% molar fraction of propylene-derived units and 10% to 40% molar fraction of ethylene or α-olefin-derived units.

[0018] Preferably, the propylene / ethylene or propylene / α-olefin copolymer contains 70% to 90% molar fraction of propylene-derived units and 10% to 30% molar fraction of ethylene or α-olefin-derived units.

[0019] Preferably, the propylene / ethylene or propylene / α-olefin copolymer contains 80% to 90% molar fraction of propylene-derived units and 10% to 20% molar fraction of ethylene or α-olefin-derived units.

[0020] Preferably, the α-olefin monomer is a C4-20 olefin-based monomer. It is noteworthy that, for certain examples, it may include one or more of 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-decene; in certain embodiments, it may simultaneously contain ethylene and α-olefin.

[0021] Preferably, the comonomer other than propylene in the propylene / ethylene or propylene / α-olefin copolymer is one or more of ethylene, 1-hexene or 1-octene;

[0022] Preferably, the comonomer other than propylene in the propylene / ethylene or propylene / α-olefin copolymer is ethylene.

[0023] Typically, the density of olefin-based polymers is affected by the type and quantity of monomers used during polymerization, the degree of polymerization, and other factors, and the copolymer is greatly influenced by the amount of comonomer. With increasing comonomer content, propylene / ethylene or propylene / α-olefin copolymers with low density can be prepared, and the type and quantity of comonomers introduced into the copolymer largely depend on the copolymerization performance of the catalytic system.

[0024] In this invention, the polymer density test method is the ASTM D792-2021 test method. Preferably, the density range of the propylene / ethylene or propylene / α-olefin copolymer described in this invention is 0.860 g / cm³. 3 Up to 0.885 g / cm 3 ;

[0025] Preferably, the density range of the propylene / ethylene or propylene / α-olefin copolymer of the present invention is 0.860 g / cm³. 3 Up to 0.880 g / cm 3 .

[0026] Unless otherwise specified, in this invention, a differential scanning calorimeter (DSC) is used to measure the crystallization temperature and melting temperature of propylene / ethylene or propylene / α-olefin copolymers. The testing procedure is described as follows: First, the copolymer is heated to 200°C and held for 5 minutes to eliminate thermal history. Then, it is cooled to -60°C and reheated to 200°C. The heating and cooling rates throughout the entire testing process are controlled at 10°C / min. The measurement result during the second heating process is calibrated as the melting temperature, and the measurement result during the third cooling process is calibrated as the crystallization temperature.

[0027] The propylene / ethylene or propylene / α-olefin copolymers according to embodiments of the present invention have a crystallization temperature (Tc) of 10°C to 110°C.

[0028] Preferably, the crystallization temperature range of the propylene / ethylene or propylene / α-olefin copolymer of the present invention is 10°C to 100°C;

[0029] Preferably, the crystallization temperature range of the propylene / ethylene or propylene / α-olefin copolymer of the present invention is 10°C to 90°C.

[0030] As described above, in this invention, a large amount of comonomer (ethylene or α-olefin) can be introduced using a transition metal compound catalytic system. As a result, as described above, the propylene / ethylene or propylene / α-olefin copolymers according to embodiments of the present invention have suitable molecular weight Mw, density, and molecular weight distribution. The olefin copolymers can be prepared using catalyst compositions of metallocene or non-metallocene transition metal compounds. The metallocene or non-metallocene transition metal compounds can be selected from any of the following compounds:

[0031]

[0032] It should be noted that the metallocene or non-metallocene transition metal compounds described in this invention are not limited to the examples above.

[0033] Meanwhile, in the preparation of propylene / ethylene or propylene / α-olefin copolymers according to embodiments of the present invention, the catalytic system may further include a co-catalyst for activating the above metallocene or non-metallocene transition metal compounds, wherein the co-catalyst is one or more substances having the following chemical formulas.

[0034] Chemical formula R 17 -[Al(R 18 )-O] n -R 19 R 17 R 18 and R 19 Each is independently any one of hydrogen, halogen, hydrocarbon group having 1 to 20 carbon atoms, and hydrocarbon group having 1 to 30 carbon atoms substituted by halogen, where n is an integer greater than 2.

[0035] Chemical formula D(R) 20 )3, D is aluminum or boron, R 20 Each of the following is independently a halogen, a hydrocarbon group having 1 to 20 carbon atoms, or a hydrocarbon group having 1 to 20 carbon atoms that has been substituted with a halogen;

[0036] Chemical formula [LH] + [Z(A)4] - Or [L] + [Z(A)4] - L is a neutral or cationic Lewis base, H is a hydrogen atom, Z is a group 13 element, and A is each independently a hydrocarbon group having 1 to 20 carbon atoms; a hydrocarbon oxygen group having 1 to 20 carbon atoms; and a substituent wherein at least one hydrogen atom of the above substituents is replaced by at least one substituent of a halogen, a hydrocarbon oxygen group having 1 to 20 carbon atoms, and a hydrocarbon silyl group having 1 to 20 carbon atoms.

[0037] More specifically, the co-catalyst is chemically formulated as R 17 -[Al(R 18 )-O] n -R 19 The compounds are preferably based on alkylaluminoxanes, such as methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane, or tert-butylaluminoxane.

[0038] In addition, the chemical formula D(R) 20Specific examples of compounds of 3 may include trimethylaluminum, triethylaluminum, triisobutylaluminum, tripropylaluminum, tributylaluminum, dimethylaluminum chloride, triisopropylaluminum, trisec-butylaluminum, tricyclopentylaluminum, tripentylaluminum, triisopentylaluminum, trihexylaluminum, trioctylaluminum, ethyldimethylaluminum, methyldiethylaluminum, triphenylaluminum, tri-p-tolylaluminum, dimethylmethoxyaluminum, dimethylethoxyaluminum, trimethylboron, triethylboron, triisobutylboron, tripropylboron or tributylboron, and particularly, may be selected from trimethylaluminum, triethylaluminum or triisobutylaluminum.

[0039] Additionally, the chemical formula [LH] + [Z(A)4] - Or [L] + [Z(A)4] -The compounds include trisubstituted ammonium salts, dialkylammonium salts, or trisubstituted phosphonium salts of borate-based compounds. More specific examples include trisubstituted ammonium salt-type borate-based compounds, such as trimethylammonium tetraphenylborate, methyl di(octadecyl)ammonium tetraphenylborate, triethylammonium tetraphenylborate, tripropylammonium tetraphenylborate, tri(n-butyl)ammonium tetraphenylborate, methyltetradecyl octadecylammonium tetraphenylborate, N,N-dimethylphenylammonium tetraphenylborate, N,N-diethylphenylammonium tetraphenylborate, N,N-dimethyl(2,4,6-trimethylphenylammonium)tetraphenylborate, and trimethylammonium tetra(pentafluorophenyl)borate. Methyl di(tetradecyl)ammonium tetra(pentafluorophenyl)borate, methyl di(octadecyl)ammonium tetra(pentafluorophenyl)borate, triethylammonium tetra(pentafluorophenyl)borate, tripropylammonium tetra(pentafluorophenyl)borate, tri(n-butyl)ammonium tetra(pentafluorophenyl)borate, trisec-butylammonium tetra(pentafluorophenyl)borate, N,N-dimethylphenylammonium tetra(pentafluorophenyl)borate, N,N-diethylphenylammonium tetra(pentafluorophenyl)borate, N,N-dimethyl(2,4,6-trimethylphenylammonium)tetra(pentafluorophenyl)borate, trimethylammonium tetra(2, 3,4,6-Tetrafluorophenyl)borate, triethylammonium tetra(2,3,4,6-tetrafluorophenyl)borate, tripropylammonium tetra(2,3,4,6-tetrafluorophenyl)borate, tri(n-butyl)ammonium tetra(2,3,4,6-tetrafluorophenyl)borate, dimethyl(tert-butyl)ammonium tetra(2,3,4,6-tetrafluorophenyl)borate, N,N-dimethylphenylammonium tetra(2,3,4,6-tetrafluorophenyl)borate, N,N-diethylphenylammonium tetra(2,3,4,6-tetrafluorophenyl)borate, N,N-dimethyl-(2,4,6-tetrafluorophenyl)borate -Trimethylphenylammonium)tetra(2,3,4,6-tetrafluorophenyl)borate, etc.; dialkylammonium salt type borate-based compounds, such as di(octadecyl)ammonium tetra(pentafluorophenyl)borate, di(tetradecyl)ammonium tetra(pentafluorophenyl)borate, di(cyclohexyl)ammonium tetra(pentafluorophenyl)borate, etc.; or trisubstituted phosphonium salt type borate-based compounds, such as triphenylphosphonium tetra(pentafluorophenyl)borate, methyl di(octadecyl)phosphonium tetra(pentafluorophenyl)borate, tri(2,6-dimethylphenyl)phosphonium tetra(pentafluorophenyl)borate, etc.

[0040] In addition, during the polymerization reaction, an organoaluminum compound may optionally be injected into the reactor to remove moisture, and the polymerization reaction may be carried out in the presence of said compound. Specific examples of such organoaluminum compounds may include trialkylaluminum, dialkylaluminum halide, alkylaluminum dihalide, dialkylaluminum hydride, or alkylsesquihalide, and more specific examples may include Al(C2H5)3, Al(C2H5)2H, Al(C3H7)3, Al(C3H7)2H, Al(i-C4H9)2H, Al(C8H5)2H, etc. 17 3. Al(C)12 H 25 3. Al(C2H5)(C 12 H 25 )2、Al(i-C4H9)(C 12 H 25 2. Al(i-C4H9)2H, Al(i-C4H9)3, (C2H5)2AlCl, (i-C3H9)2AlCl, or (C2H5)3Al2Cl3. These organoaluminum compounds can be continuously injected into the reactor, and to properly remove impurities such as water and oxygen, the organoaluminum compounds can be injected at a ratio of approximately 0.1 to 10 mol / kg of the reaction medium in the reactor.

[0041] In some embodiments, the propylene / ethylene or propylene / α-olefin copolymer is obtained by polymerizing propylene with one or more of ethylene or α-olefins in one or more polymerization reactors;

[0042] In some embodiments, the polymerization reactor is one or more of a non-stirred or stirred cylindrical container, a tank container, and a circulating loop reactor;

[0043] In some embodiments, when the polymerization reactor is a stirred cylindrical container or a tank container, adjusting the length-to-diameter ratio or the circulation ratio of the reactor will result in temperature and concentration distribution of the material entering the reactor. This further enables the adjustment of the composition and structure of the polymer generated in different temperature regions of the microscopic area, and ultimately achieves the generation of the polymer with the specific properties described in this invention.

[0044] In some embodiments, when the polymerization reactor is a circulating loop reactor, the composition and structure of the polymer generated in different temperature regions of the micro-region are further adjusted by adjusting the ratio of the circulation volume of the reactor circulation pump per unit time to the reactor volume, i.e., the circulation ratio, which ultimately enables the generation of polymers with the specific properties described in the claims.

[0045] In some embodiments, the reaction temperature of the polymerization reaction is 20°C to 200°C, preferably 50°C to 200°C, more preferably 70°C to 180°C, even more preferably 90°C to 180°C, and even more preferably 110°C to 180°C.

[0046] In some embodiments, the reaction pressure of the polymerization reaction is 10 bar to 100 bar, preferably 10 bar to 80 bar, more preferably 30 bar to 80 bar, and even more preferably 30 bar to 60 bar.

[0047] Preferably, the density range of the propylene / ethylene or propylene / α-olefin copolymer of the present invention is 0.860 g / cm³. 3 Up to 0.880 g / cm 3 .

[0048] In some embodiments, when the polymerization reactor is a stirred cylindrical container or a tank container, the length-to-diameter ratio of the reactor is 5:1 to 20:1, preferably 5:1 to 10:1.

[0049] In some embodiments, when the polymerization reactor is a circulating loop reactor, the circulation ratio of the reactor is 100 to 1000, preferably 10:1 to 80:1.

[0050] It should be noted that the feeding sequence of the polymerization reaction is as follows:

[0051] ① First, introduce a solvent into the reaction system;

[0052] ② A pre-mixed stream of propylene, ethylene, and C6 isoalkane solvent is homogenized in a mixer, and then introduced into the reactor via a cooler.

[0053] ③ Once the concentration in the reactor is uniform and stable, a mixed flow of the main catalyst and co-catalyst, which has been pre-mixed evenly in the mixer, is introduced into the reactor to initiate the polymerization reaction.

[0054] The beneficial effects of this invention are as follows: Based on the propylene-based copolymer of this invention, when used as an additive in the heat-sealing layer of CPP cast film, due to its defined ∑ΔH... T It exhibits properties that improve the tear strength and drop impact resistance of composite membrane materials. Detailed Implementation

[0055] Example

[0056] Examples of catalyst synthesis: For the synthesis of catalyst I with similar structures, please refer to patents US20040014950A1, CN116554378A, CN114230702B, CN116212960A and literature J.Am.Chem.Soc.2010,132,5566–5567, etc.; For the synthesis of catalyst II, please refer to patents US6057408A, CN117777183A and literature J.Am.Chem.Soc.1998,120,2308-2321 and Organometallics 1994,13,954-963, etc.

[0057] The polymerization examples below use Zr-4 as the main catalyst.

[0058] Polymerization Example: A small-scale continuous polymerization reactor was used for the polymerization experiment. The polymerization reaction was solution polymerization, and the reaction unit was a multi-reactor series polymerization reaction. The reactor volume was 500 mL, the length-to-diameter ratio was 5:1, and the full-load capacity of the unit was 1 kg polymer / hour. Before the reaction started, the reactor and pipeline jacket of the continuous polymerization reactor were heated to 150°C, and the reactor was stirred and heated. After the temperature reached the set temperature, the feed pump was started to begin feeding Isohexanes at a rate of 5.0 L / h. The purpose of the oil flushing was to rinse away any residual polymer and other impurities in the polymerization reactor and material conveying pipeline. The oil flushing lasted for half an hour. The solvent feed rate was adjusted to 2.6 L / h, the propylene feed rate to 1350 g / h, the ethylene feed rate to 60 g / h, the Zr-4 main catalyst feed rate to 7.0 μmol / h, the co-catalyst 1 was triisobutylaluminum (TIBA) diluted 120 times with an Al / M ratio of 500, and the co-catalyst 2 was N,N-dimethylphenylammonium tetra(pentafluorophenyl)borate diluted 120 times with a B / M ratio of 1.3. The reaction pressure was 3 MPa. After the temperature stabilized, the main catalyst was added to initiate polymerization. After the polymerization reaction stabilized, the polymer, after quenching and flash devolatilization, was collected and its properties were characterized.

[0059] The polymer density was measured according to ASTM D-792; the polymer melt index (MI) was measured according to ASTM D-1238 (190°C, 2.16 kg load); the polymer melt temperature (Tm) was obtained using a PerkinElmer Differential Scanning Calorimeter (DSC) 6000. Specifically, the temperature was raised to 200°C, held at that temperature for 1 minute, then lowered to -100°C, and the temperature was raised again to obtain the top of the DSC curve as the melting point. At this point, the temperature rise and fall rate was 10 °C / min, and the melting point was obtained during the second temperature rise. The weight-average molecular weight (Mw, g / mol) and molecular weight distribution (MWD) were measured by gel permeation chromatography (GPC) for the number-average molecular weight (Mn) and weight-average molecular weight (Mw), respectively, and the molecular weight distribution was calculated by dividing the weight-average molecular weight by the number-average molecular weight. The chromatographic column was PL Olexis, the solvent was trichlorobenzene (TCB), the flow rate was 1.0 ml / min, the sample concentration was 1.0 mg / ml, the injection volume was 200 μl, the column temperature was 160 °C, the detector was an Agilent high-temperature RI detector, and the standard was polystyrene (calibrated using a cubic function).

[0060] [Table 1]

[0061]

[0062]

[0063] *Example 7: The comonomer is a propylene / 1-octene copolymer.

[0064] [Table 2]

[0065]

[0066] * T represents the melting peak temperature of the segmented melting range measured by SSA, 85℃≤T≤120℃; Example 7: The comonomer is propylene / 1-octene copolymer.

[0067] Table 1 shows the continuous polymerization reaction process conditions, and Table 2 shows the basic performance characterization results of the corresponding polymer samples. It can be seen that adjusting the C3 / C2 monomer ratio and polymerization temperature conditions results in a polymer density range of 0.861 g / cm³ to 0.871 g / cm³. 3 The density falls within the typical range for polyolefin elastomer materials. Overall, the melt index is inversely proportional to Mw; the polymerization products consistently maintain a narrow distribution, with PDI < 3; the ethylene insertion rate (wt%) is inversely proportional to the C3 / C2 monomer ratio, meaning that the more C2 monomers are added, the higher the ethylene insertion rate (wt%) of the polymer sample, and vice versa; under all polymerization conditions, γ (%) is greater than 90, which is significantly different from Comparative Examples 1 and 2, where γ (%) is 60 and 7, respectively.

[0068] [Table 3]

[0069]

[0070]

[0071] The propylene-based copolymer of the present invention is used as an additive in the heat-sealing layer of CPP cast film, due to its defined ∑ΔH T It exhibits properties that improve the tear strength and drop impact resistance of composite membrane materials.

[0072] As shown in Table 3, the CPP cast film base material was Yanshan Petrochemical's ternary copolymer polypropylene F5606. Each polymer prepared in Examples 1-7 and Comparative Examples 1 and 2 was mixed at 15% and the cast film base material F5606 at 85% and then extruded and cast into a film. The tear strength and drop-mark impact properties of each film material were tested. It can be seen that the addition of elastomer materials in Examples 1-7 effectively improved the tear strength and drop-mark impact properties of the composite film materials.

[0073] Comparing Examples 1, 2, and 3 in Table 3, we can conclude that increasing the ethylene content in the polymer product can more effectively improve the tear strength and drop impact of the substrate. However, it is speculated that an excessively high comonomer content will make the composite film "softer," affecting its processing performance and rigidity. Comparing Examples 1, 4, 5, and 6 in Table 3, we can conclude that increasing the molecular weight of the polymer product can also effectively improve the tear strength and drop impact of the substrate.

[0074] Comparing Example 1, Comparative Example 1, and Comparative Example 2 in Table 3, the tear strength and drop impact strength of the comparative composite film materials decreased significantly, even lower than those of the base material. When ∑ΔH T / ΔH 总 When the content is less than 90%, the melting range of propylene / ethylene or propylene / α-olefin copolymers widens, further affecting the room temperature performance of composite membrane materials.

Claims

1. A copolymer of propylene / ethylene or propylene / α-olefin, said copolymer having the following characteristics: (a) Molecular weight Mw: 2.0 × 10 4 g / mol ~ 40.0 × 10 4 g / mol; (b) Density: 0.860 to 0.890 g / cm³ 3 ; (c) Molecular weight distribution Mw / Mn: 2.0 to 4.0; (d) ∑∆H measured continuously using differential scanning calorimetry (DSC) with self-nucleation / annealing SSA T ≤4J / g, where T represents the melting peak temperature of the segmented melting range measured by SSA, 85℃≤T≤120℃; and ∑∆H T / ∆H 总 ≥90%; The melting temperature of propylene / ethylene or propylene / α-olefin copolymers is measured using a differential scanning calorimeter (DSC): that is, after raising the temperature to 200°C, holding it at that temperature for 1 minute, then lowering it to -100°C, and raising the temperature again to obtain the top of the DSC curve as the melting point, with the temperature rising and falling at a rate of 10°C / min, and obtaining the melting point during the second temperature rise.

2. The copolymer according to claim 1, characterized in that, The weight-average molecular weight range of the propylene / ethylene or propylene / α-olefin copolymer is 3 × 10⁻⁶. 4 g / mol ~35.0×10 4 g / mol; and / or, the molecular weight distribution range of the propylene / ethylene or propylene / α-olefin copolymer is 2.5 to 3.

5.

3. The copolymer according to claim 2, characterized in that, The weight-average molecular weight range of the propylene / ethylene or propylene / α-olefin copolymer is 3 × 10⁻⁶. 4 g / mol ~ 30.0 × 10 4 g / mol.

4. The copolymer according to claim 1, characterized in that, The propylene / ethylene or propylene / α-olefin copolymer contains 50% to 97% molar fraction of propylene-derived units and 3% to 50% molar fraction of ethylene or α-olefin-derived units.

5. The copolymer according to claim 4, characterized in that, The propylene / ethylene or propylene / α-olefin copolymer contains 60% to 90% molar fraction of propylene-derived units and 10% to 40% molar fraction of ethylene or α-olefin-derived units.

6. The copolymer according to claim 4, characterized in that, The propylene / ethylene or propylene / α-olefin copolymer contains 70% to 90% molar fraction of propylene-derived units and 10% to 30% molar fraction of ethylene or α-olefin-derived units.

7. The copolymer according to claim 4, characterized in that, The propylene / ethylene or propylene / α-olefin copolymer contains 80% to 90% molar fraction of propylene-derived units and 10% to 20% molar fraction of ethylene or α-olefin-derived units.

8. The copolymer according to any one of claims 1-7, characterized in that, The α-olefin monomer is a C4-20 olefin-based monomer.

9. The copolymer as claimed in claim 8, characterized in that, The monomer of the α-olefin is one or more of 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-decene.

10. The method for preparing the copolymer of propylene / ethylene or propylene / α-olefin as described in any one of claims 1-9, characterized in that, The process includes the following steps: polymerizing propylene with one or more of ethylene or α-olefins in one or more polymerization reactors, wherein the polymerization reactor is a stirred cylindrical container or a tank container, and the length-to-diameter ratio of the reactor is 5:1 to 10:

1.

11. The preparation method according to claim 10, characterized in that, The method is carried out in the presence of a transition metal compound catalyzed system, wherein the transition metal compound is selected from any one of the following compounds:

12. The preparation method according to claim 10 or 11, characterized in that, The method is carried out in the presence of a co-catalyst, which is one or more substances having the following chemical formulas: Chemical formula R 17 -[Al(R 18 )-O] n -R 19 R 17 R 18 and R 19 Each is independently any one of hydrogen, halogen, hydrocarbon group having 1 to 20 carbon atoms, and hydrocarbon group having 1 to 30 carbon atoms substituted by halogen, where n is an integer greater than 2. Chemical formula D(R) 20 )3, D is aluminum or boron, R 20 Each of the following is independently a halogen, a hydrocarbon group having 1 to 20 carbon atoms, or a hydrocarbon group having 1 to 20 carbon atoms that has been substituted with a halogen; Chemical formula [LH] + [Z(A)4] - Or [L] + [Z(A)4] - L is a neutral or cationic Lewis base, H is a hydrogen atom, Z is a group 13 element, and A is each independently a hydrocarbon group having 1 to 20 carbon atoms; a hydrocarbon oxygen group having 1 to 20 carbon atoms; and a substituent wherein at least one hydrogen atom of the above substituents is replaced by at least one substituent of a halogen, a hydrocarbon oxygen group having 1 to 20 carbon atoms, and a hydrocarbon silyl group having 1 to 20 carbon atoms.

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