Propylene-ethylene copolymers, process for their preparation and use

Abstract

This application relates to the field of olefin polymerization technology, specifically to propylene-ethylene copolymers, their preparation methods, and applications. The monomers of the propylene-ethylene copolymer are ethylene and propylene, and the propylene-ethylene copolymer satisfies the following characteristics: (i) a weight-average molecular weight of 150,000-250,000; (ii) the molar percentage of propylene-propylene-propylene segments in the propylene-ethylene copolymer is n1, the molar percentage of propylene-ethylene-propylene segments is n2, and 5 ≤ n1 / n2 ≤ 7.5. This propylene-ethylene copolymer has a low initial sealing temperature and high heat-sealing strength, while also possessing good mechanical properties.

Description

Technical Field

[0001] This application relates to the field of olefin polymerization technology, and in particular to propylene-ethylene copolymers, their preparation methods, and applications. Background Technology

[0002] Polypropylene (PP) is a thermoplastic widely used in the packaging industry, with cast polypropylene (CPP) film being one of its important applications. In CPP film, the heat-sealing layer material plays a crucial role in the heat-sealing performance of the packaging. Propylene-based copolymers, especially those containing ethylene monomers, are widely used as heat-sealing layers in CPP films due to their adjustable melting points and excellent heat-sealing properties.

[0003] Traditional propylene-based copolymers containing ethylene monomers present a challenge in simultaneously achieving the desired heat-sealing temperature, maintaining heat-sealing strength, and preserving the mechanical properties of the heat-sealing layer material, creating a conflicting situation. Furthermore, propylene-based copolymers containing ethylene monomers have relatively high melting temperatures, requiring a longer cooling and sealing time during the heat-sealing process.

[0004] Currently, the sealing temperature and heat-sealing strength of materials are mainly improved by adjusting the types and proportions of comonomers. However, how to maintain a low sealing temperature while simultaneously achieving high heat-sealing strength and good mechanical properties remains a pressing technical problem to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, one or more embodiments of this application provide propylene-ethylene copolymers, their preparation methods, and applications. These propylene-ethylene copolymers exhibit low initial sealing temperature and high heat-sealing strength, while also possessing good mechanical properties.

[0006] One or more embodiments of this application provide propylene-ethylene copolymers, wherein the monomers of the propylene-ethylene copolymers are ethylene and propylene, and the propylene-ethylene copolymers satisfy the following characteristics:

[0007] (i) Weight-average molecular weight is 150,000-250,000;

[0008] (ii) The molar percentage of propylene-propylene-propylene segments in the propylene-ethylene copolymer is n1, and the molar percentage of propylene-ethylene-propylene segments is n2, where 5 ≤ n1 / n2 ≤ 7.5.

[0009] In some embodiments, the melting temperature is 60°C-90°C.

[0010] In some embodiments, 60% ≤ n1 ≤ 75%.

[0011] In some embodiments, 10% ≤ n2 ≤ 12%.

[0012] In some embodiments, the density of the propylene-ethylene copolymer is 0.86 g / cm³. 3 -0.885g / cm 3 .

[0013] In some embodiments, the polydispersity index of the propylene-ethylene copolymer is 2-4.

[0014] In some embodiments, the ethylene segment in the propylene-ethylene copolymer accounts for 1%-15% by mass.

[0015] One or more embodiments of this application provide a method for preparing a propylene-ethylene copolymer, which can be used to prepare the propylene-ethylene copolymer described above. The description of this preparation method is merely illustrative and intended to help those skilled in the art better understand the technical solutions of this application, and is not intended to be the sole limitation of the preparation method of this application.

[0016] In some embodiments, the preparation method of the propylene-ethylene copolymer includes the following steps:

[0017] The preparation is carried out using a continuous reaction apparatus, which includes a mixing tank and a reaction tank connected together.

[0018] Materials including propylene, ethylene, co-catalyst and solvent are continuously fed into a mixing tank and stirred at a first pressure and a first temperature.

[0019] The material output from the mixing tank and the main catalyst are continuously fed into the reaction tank, and the reaction tank is stirred under a second pressure and a second temperature to obtain the propylene-ethylene copolymer.

[0020] The ratio of the average residence time of the material in the mixing tank to the average residence time in the reaction tank is (2-6):1;

[0021] The first pressure is 0.1-10 MPa, and the first temperature is 10℃-50℃;

[0022] The second pressure is 1-10 MPa, and the second temperature is 70℃-200℃.

[0023] In some embodiments, the volume ratio of the mixing tank to the reaction tank is (2-6):1; preferably, it is (3-4):1.

[0024] In some embodiments, the first pressure is 1 MPa-5 MPa, and the first temperature is 20°C-40°C.

[0025] In some embodiments, the second pressure is 2MPa-6MPa, and the second temperature is 80℃-170℃.

[0026] In some embodiments, the length-to-diameter ratio of the mixing tank is (1-5):1.

[0027] In some embodiments, the length-to-diameter ratio of the reaction vessel is (1-5):1.

[0028] In some embodiments, the conditions for the first stirring include: a stirring speed of 100 rpm to 600 rpm.

[0029] In some embodiments, the conditions for the second stirring include: a stirring speed of 300 rpm to 800 rpm.

[0030] In some embodiments, the main catalyst comprises one or more of a metallocene catalyst and a non-metallocene catalyst.

[0031] In some embodiments, the metallocene catalyst comprises one or more of the following: rac-ethylene bis(1-indenyl)zirconia, racemic dimethylsilyl bis(1-indenyl)zirconia, diphenylmethylene(cyclopentadiene)(9-fluorenyl)zirconia, dimethyldimethylsilyl bis(2-methyl-4-phenyl-1-indenyl)zirconia, bis(methylcyclopentadiene)zirconia, bis(1,3-dimethylcyclopentadienyl)zirconia, dimethylsilyl bis(2-methyl-4-phenylindenyl)zirconia, (cyclopentadienyl)(1,2-dimethoxyethane)zirconia trichloride, diphenylmethylenecyclopentadiene(2,7-di-tert-butyl-fluorenyl)zirconia, dimethyl bis(propylcyclopentadienyl)hafnium, and bis(n-butylcyclopentadiene)hafnium.

[0032] In some embodiments, the non-metallocene catalyst comprises one or more of the compounds shown in Formula I and Formula II;

[0033] Formula I

[0034] Formula II

[0035] R1, R2, R6, and R7 are each independently selected from C1-C atoms that have undergone hydrogen or halogen substitution. 10 Alkyl, amino substituted C1-C 10 Alkyl or C1-C 10 alkyl;

[0036] R3, R4, R5, R8, R9 and R 10 Each is independently selected from C1-C cells substituted with hydrogen or halogen. 10 Alkyl, amino substituted C1-C 10 Alkyl, C1-C 10 Alkyl, substituted or unsubstituted C6-C 10 Aryl;

[0037] Q1 and Q2 are each independently selected from halogen-substituted C1-C 10 Alkyl, amino substituted C1-C 10 Alkyl, C1-C 10 Alkyl or halogen-substituted C6-C 10 Aryl and amino substituted C6-C 10 Aryl or C6-C 10 Aryl;

[0038] Y is selected from carbon or silicon;

[0039] X1 and X2 are each independently selected from halogenated, amino, or halogenated C1-C groups. 10 Alkyl, amino substituted C1-C 10 Alkyl or C1-C 10 alkyl;

[0040] M is selected from group IVB metals.

[0041] In some embodiments, the cocatalyst includes an aluminum additive, and optionally, also includes a boron additive.

[0042] In some embodiments, the amount of aluminum additive added is based on the molar ratio Al / M of metallic aluminum and metallic M in the main catalyst, where Al / M is 1-3000.

[0043] In some embodiments, the amount of boron additive added is calculated as the molar ratio of boron to metal M in the main catalyst, B / M, where B / M is 0-10.

[0044] In some embodiments, the solvent includes one or more of alkane solvents, aromatic solvents, cycloalkanes solvents, and haloalkanes solvents.

[0045] In some embodiments, the main catalyst comprises 0.00001%-0.0009% by mass of the material in the reaction vessel.

[0046] In some embodiments, the mass ratio of propylene to the solvent is (0.2-0.9):1.

[0047] In some embodiments, the mass percentage of ethylene is 3%-20% based on the total mass of ethylene and propylene being 100%.

[0048] One or more embodiments of this application provide the application of the propylene-ethylene copolymer described above or the propylene-ethylene copolymer prepared by the preparation method described above in the preparation of heat-sealing materials.

[0049] This application controls the weight-average molecular weight of the propylene-ethylene copolymer to be between 150,000 and 250,000, and the melting temperature to be between 60°C and 90°C. Simultaneously, the ratio n1 / n2 of the molar percentage of PPP (propylene-propylene-propylene) segments (n1) to that of PEP (propylene-ethylene-propylene) segments (n2) is controlled between 5 and 7.5. Controlling the weight-average molecular weight to 150,000-250,000 provides sufficient molecular chain entanglement density to ensure high heat-sealing strength and mechanical properties, while avoiding poor processing flowability and increased initial sealing temperature due to excessively high molecular weight, and also avoiding insufficient heat-sealing strength due to excessively low molecular weight. Controlling n1 / n2 to 5-7.5 means controlling the relative proportions of PEP and PPP segments within a suitable range. PEP segments are the structural units of the amorphous region of the copolymer; the insertion of ethylene units disrupts the regularity of the polypropylene molecular chains, reducing the crystallinity and melting point of the copolymer. PPP segments are the main structural units of the crystalline region of the copolymer. The crystallinity and rigidity of the copolymer are determined by the n1 / n2 ratio. When n1 / n2 is between 5 and 7.5, the copolymer has sufficient crystalline structure to maintain good mechanical properties (such as tensile strength and flexural modulus). A suitable amount of ethylene is uniformly dispersed in the form of PEP, which effectively reduces the initial sealing temperature. At the same time, the EP network formed by PEP segments in the amorphous region promotes the interdiffusion and entanglement of molecular chains during the heat sealing process, thereby achieving high heat seal strength at a lower temperature. With the synergistic effect of a suitable weight-average molecular weight and the proportion of PPP and PEP segments, this propylene-ethylene copolymer achieves a balance between low initial sealing temperature, high heat seal strength, and good mechanical properties.

[0050] The method for preparing propylene-ethylene copolymers disclosed in this application achieves effective control over the copolymer segment sequence distribution and molecular weight by precisely controlling the volume ratio of the mixing tank to the reaction tank, the premixing pressure and temperature, and the polymerization reaction pressure and temperature. This results in the preparation of propylene-ethylene copolymers that meet the aforementioned requirements: a PPP segment content n1 to PEP segment content n2 ratio of 5-7.5, a weight-average molecular weight of 150,000-250,000, and a melting temperature of 60℃-90℃. This preparation method is simple to operate, can be used in continuous industrial production, and can yield propylene-ethylene copolymers with low initial sealing temperature, high heat-sealing strength, and good mechanical properties. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0052] Figure 1This is a process flow diagram of one embodiment of this application. Detailed Implementation

[0053] The present application is further described below with reference to embodiments and examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Furthermore, it should be understood that after reading the teachings of this application, those skilled in the art can make various alterations or modifications to this application, and these equivalent forms also fall within the protection scope of the appended claims.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0055] The term "and / or" as used herein includes any one of two or more related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations encompass any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and A+B.

[0056] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0057] In this application, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, optional numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval points to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges may be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0058] In this application, weight can be a well-known unit of mass in the chemical industry, such as μg, mg, g, or kg.

[0059] In this application, the reaction pressure refers to the "gauge pressure of the reaction vessel".

[0060] One or more embodiments of this application provide propylene-ethylene copolymers, wherein the monomers of the propylene-ethylene copolymers are ethylene and propylene, and the propylene-ethylene copolymers satisfy the following characteristics:

[0061] (i) Weight-average molecular weight is 150,000-250,000;

[0062] (ii) The molar percentage of propylene-propylene-propylene segment (PPP) in the propylene-ethylene copolymer is n1, and the molar percentage of propylene-ethylene-propylene segment (PEP) is n2, where 5 ≤ n1 / n2 ≤ 7.5.

[0063] The propylene-ethylene copolymer of this application embodiment has a weight-average molecular weight controlled between 150,000 and 250,000, which provides sufficient molecular chain entanglement density to ensure high heat-sealing strength and mechanical properties, while avoiding poor processing fluidity and increased sealing temperature caused by excessively high molecular weight, and also avoiding insufficient heat-sealing strength caused by excessively low molecular weight. The n1 / n2 ratio is controlled between 5 and 7.5, meaning the relative proportions of PEP and PPP segments are kept within a suitable range. PEP segments are the structural units of the amorphous region of the copolymer. The insertion of ethylene units disrupts the regularity of the polypropylene molecular chain, reducing the crystallinity and melting point of the copolymer. PPP segments are the main structural units of the crystalline region of the copolymer, determining its crystallinity and rigidity. When n1 / n2 is between 5 and 7.5, the copolymer has sufficient crystalline structure to maintain good mechanical properties (such as tensile strength and flexural modulus). A suitable amount of ethylene is uniformly dispersed in the form of PEP, effectively reducing the initial sealing temperature. At the same time, the EP network formed by PEP segments in the amorphous region promotes the interdiffusion and entanglement of molecular chains during heat sealing, thereby achieving high heat-sealing strength at a lower temperature. With the synergistic effect of a suitable weight-average molecular weight and the proportions of PPP and PEP segments, this propylene-ethylene copolymer achieves a balance between low initial sealing temperature, high heat-sealing strength, and good mechanical properties.

[0064] In some embodiments, the weight-average molecular weight of the propylene-ethylene copolymer can be selected from 150,000 to 250,000, for example, 150,000, 180,000, 200,000, 220,000, 250,000, etc.

[0065] The melting temperature is related to the ratio of PEP and PPP segments. In some embodiments, the melting temperature of the propylene-ethylene copolymer is 60℃-90℃, for example, 60℃, 70℃, 80℃, 90℃, etc.

[0066] In some embodiments, 5 ≤ n1 / n2 ≤ 7.5, meaning n1 / n2 is any value between 5 and 7.5, such as 5, 5.5, 6, 6.5, 7, 7.5, etc. When the ratio is less than 5, the polymer has more PEP segments, which significantly reduces the heat-sealing temperature. However, the number of crystallizable PPP segments is less, resulting in less crystalline portion in the heat-sealed region and thus lower heat-sealing strength. When the ratio is greater than 7.5, the copolymer has more PPP segments, resulting in a higher melting point and a higher heat-sealing temperature. Preferably, 5.6 ≤ n1 / n2 ≤ 6.4.

[0067] In some embodiments, n1 can be selected from 60%-75%, for example, it can be 60%, 65%, 70%, 75%, etc. Preferably, 64%≤n1≤70%. In this embodiment, n1 is 60%-75%, and the copolymer has a sufficient crystalline structure to maintain good mechanical properties (such as tensile strength and flexural modulus).

[0068] In some embodiments, n2 can be selected from 10%-12%, for example, 10.7%, 11%, 12%, etc. Preferably, 11%≤n2≤12%. In this embodiment, n2 is 10%-12%, and an appropriate amount of ethylene is uniformly dispersed in the form of PEP, thereby effectively reducing the initial sealing temperature. At the same time, the EP network formed by PEP segments in the amorphous region promotes the interdiffusion and entanglement of molecular chains during the heat sealing process, thereby obtaining high heat sealing strength at a lower temperature.

[0069] In some embodiments, the density of the propylene-ethylene copolymer is 0.86 g / cm³. 3 -0.885g / cm 3 For example, it can be 0.86 g / cm³. 3 0.865g / cm 3 0.87g / cm 3 0.875g / cm 3 0.88g / cm 3 0.885g / cm 3 wait.

[0070] In some embodiments, the polydispersity index of the propylene-ethylene copolymer is 2-4.

[0071] In some embodiments, the propylene-ethylene copolymer comprises, by weight percentage, 1%-15% ethylene segments and 85%-99% propylene segments; wherein the ethylene mass percentage is selected from 1%-15%, for example, 1%, 2%, 5%, 8%, 10%, 12%, 15%, etc., and the propylene mass percentage is selected from 85%-99%, for example, 85%, 90%, 92%, 95%, 98%, 99%, etc.

[0072] One or more embodiments of this application also provide a method for preparing a propylene-ethylene copolymer, which can be used to prepare the propylene-ethylene copolymer described above. The description of this preparation method is merely illustrative and intended to help those skilled in the art better understand the technical solutions of this application, and is not intended to be the sole limitation of the preparation method of this application.

[0073] After reading this specification, those skilled in the art can appropriately adjust or replace the order of steps, types of protecting groups, reaction reagents, reaction conditions, and combinations thereof in the following preparation methods based on actual needs, availability of raw materials, and general technical knowledge in the field. Any adjustment or substitution that achieves the preparation of the target product of this application falls within the scope of protection of this application. In other words, the process parameters, reagent selection, and order of steps described in the following specific embodiments should not be construed as limitations on this application.

[0074] In some embodiments, the preparation method of the propylene-ethylene copolymer includes the following steps:

[0075] The preparation is carried out using a continuous reaction apparatus, which includes a mixing tank and a reaction tank connected together.

[0076] S1. Materials including propylene, ethylene, co-catalyst and solvent are continuously fed into the mixing tank and stirred at a first pressure and a first temperature.

[0077] S2. The material output from the mixing tank and the main catalyst are continuously fed into the reaction tank, and the reaction tank is stirred under a second pressure and a second temperature to obtain the propylene-ethylene copolymer.

[0078] The ratio of the average residence time of the material in the mixing tank to the average residence time in the reaction tank is (2-6):1 (for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, etc.).

[0079] The first pressure is 0.1-10MPa (e.g., it can be 0.1MPa, 0.5MPa, 1MPa, 2MPa, 5MPa, 8MPa, 10MPa, etc.), and the first temperature is 10℃-50℃ (e.g., it can be 10℃, 20℃, 30℃, 40℃, 50℃, etc.).

[0080] The second pressure is 1-10MPa (e.g., it can be 1MPa, 2MPa, 5MPa, 8MPa, 10MPa, etc.), and the second temperature is 70℃-200℃ (e.g., it can be 70℃, 80℃, 100℃, 120℃, 150℃, 180℃, 200℃, etc.).

[0081] In this embodiment, by premixing the material in a mixing tank at a first pressure and a first temperature, and then reacting it in a reaction tank at a second pressure and a second temperature, and controlling the average residence time of the material in the mixing tank and the reaction tank, the degree of polymerization and the distribution of chain segments of the polymer can be effectively controlled within a suitable range, thereby achieving a balance between low initial sealing temperature, high heat sealing strength and good mechanical properties.

[0082] In some embodiments, when the tank is full, the residence time can be controlled by the volume of the mixing tank and the volume of the reaction vessel, wherein the volume ratio of the mixing tank to the reaction vessel is (2-6):1, for example 2:1, 3:1, 4:1, 5:1, 6:1, etc., preferably (3-4):1.

[0083] In some embodiments, the first pressure is 1 MPa-5 MPa, and the first temperature is 20°C-40°C. Premixing at this pressure and temperature allows for better control of the polymerization degree of the chain segments and the distribution of PEP and PPP chain segments within a suitable range.

[0084] In some embodiments, the second pressure is 2 MPa-6 MPa, and the second temperature is 80°C-170°C. Reacting under these pressures and temperatures allows for better control of the degree of polymerization of the chain segments and ensures that the distribution of PEP and PPP segments remains within a suitable range.

[0085] In some embodiments, the length-to-diameter ratio of the mixing tank is (1-5):1, such as 1:1, 2:1, 3:1, 4:1, 5:1, etc.

[0086] In some embodiments, the length-to-diameter ratio of the reaction vessel is (1-5):1, such as 1:1, 2:1, 3:1, 4:1, 5:1, etc.

[0087] In some embodiments, the conditions for the first stirring include: the stirring speed is 100rpm-600rpm, such as 100rpm, 200rpm, 300rpm, 400rpm, 500rpm, 600rpm, etc.

[0088] In some embodiments, the conditions for the second stirring include: the stirring speed is 300rpm-800rpm, such as 300rpm, 400rpm, 500rpm, 600rpm, 700rpm, 800rpm, etc.

[0089] In some embodiments, the main catalyst comprises one or more of a metallocene catalyst and a non-metallocene catalyst.

[0090] In some embodiments, the metallocene catalyst comprises one or more of the following: rac-ethylene bis(1-indenyl)zirconia, racemic dimethylsilyl bis(1-indenyl)zirconia, diphenylmethylene(cyclopentadiene)(9-fluorenyl)zirconia, dimethyldimethylsilyl bis(2-methyl-4-phenyl-1-indenyl)zirconia, bis(methylcyclopentadiene)zirconia, bis(1,3-dimethylcyclopentadienyl)zirconia, dimethylsilyl bis(2-methyl-4-phenylindenyl)zirconia, (cyclopentadienyl)(1,2-dimethoxyethane)zirconia trichloride, diphenylmethylenecyclopentadiene(2,7-di-tert-butyl-fluorenyl)zirconia, dimethyl bis(propylcyclopentadienyl)hafnium, and bis(n-butylcyclopentadiene)hafnium.

[0091] In some embodiments, one or more of the compounds represented by Formula I and Formula II;

[0092] Formula I

[0093] Formula II

[0094] R1, R2, R6, and R7 are each independently selected from C1-C atoms that have undergone hydrogen or halogen substitution. 10 Alkyl, amino substituted C1-C 10 Alkyl, C1-C 10 alkyl;

[0095] R3, R4, R5, R8, R9 and R 10 Each is independently selected from C1-C cells substituted with hydrogen or halogen. 10 Alkyl, amino substituted C1-C 10 Alkyl, C1-C 10 Alkyl or substituted or unsubstituted C6-C 10 The aryl group, whether substituted or unsubstituted, is independently selected from halogens, amino groups, and C1-C groups. 15 Straight-chain or branched alkyl groups, C3-C 15 cycloalkyl, silyl, C6-C 20 Aryl, C3-C 20 At least one of the heteroaryl groups.

[0096] Q1 and Q2 are each independently selected from halogen-substituted C1-C. 10 Alkyl, amino substituted C1-C 10 Alkyl, C1-C 10 Alkyl or halogen-substituted C6-C 10 Aryl and amino substituted C6-C 10 Aryl or C6-C 10 Aryl;

[0097] Y is selected from carbon or silicon;

[0098] X1 and X2 are each independently selected from halogenated, amino, or halogenated C1-C groups. 10 Alkyl, amino substituted C1-C 10 Alkyl or C1-C 10 alkyl;

[0099] M is selected from group IVB metals.

[0100] In some embodiments, the cocatalyst includes an aluminum additive, and optionally, also includes a boron additive.

[0101] In some embodiments, the amount of aluminum additive added is based on the molar ratio Al / M of metallic aluminum and metallic M in the main catalyst, where Al / M is 1-3000.

[0102] In some embodiments, the amount of boron additive added is calculated as the molar ratio of boron to metal M in the main catalyst, B / M, where B / M is 0-10.

[0103] In some embodiments, the solvent includes one or more of alkane solvents, aromatic solvents, cycloalkanes solvents, and haloalkanes solvents.

[0104] In some embodiments, the main catalyst comprises 0.00001%-0.0009% by mass of the material in the reaction vessel.

[0105] In some embodiments, the mass ratio of propylene to the solvent is (0.2-0.9):1.

[0106] In some embodiments, with the total mass of ethylene and propylene being 100%, the mass percentage of ethylene is 3%-20%. Due to the different polymerization rates of the catalyst during the synthesis of ethylene and propylene, the ethylene content is slightly excessive during preparation. In this embodiment, controlling the mass percentage of ethylene in the raw materials to 3%-20% ensures that the mass percentage of ethylene segments in the product is within a suitable range, for example, 1%-15%.

[0107] One or more embodiments of this application provide the application of the propylene-ethylene copolymer described above or the propylene-ethylene copolymer prepared by the preparation method described above in the preparation of heat-sealing materials.

[0108] The following are some specific examples.

[0109] Unless otherwise specified, all raw materials and reagents used in the following examples and comparative examples can be purchased commercially; the main sources of the raw materials are as follows:

[0110] Ethylene, polymerization grade, purchased from Air Liquide;

[0111] Propylene, polymerization grade, purchased from Air Liquide;

[0112] Industrial hexane, 99%, purchased from Sinopec;

[0113] Isopar-E, 100% hydrogenated naphtha, purchased from Mobil;

[0114] Triisobutylaluminum (TIBA) hexane solution, 1 mol / L, purchased from Inokai;

[0115] Triethylaluminum (TEA) hexane solution, 1 mol / L, purchased from Inokai;

[0116] MMAO, 7% aluminum in Isopar-E solution, purchased from Norin;

[0117] MAO, 15% aluminum Isopar-E solution, purchased from Albemarle;

[0118] Triphenylmethyltetra(pentafluorophenyl)borate, 99%, purchased from Inokai, soluble in toluene, 10 wt%;

[0119] RAC-ethylenebis(1-indenyl)zirconium dichloride, 99%, strem;

[0120] Diphenylmethylenecyclopentadiene (2,7-di-tert-butyl-fluorenyl)zirconium dichloride, 98%, purchased from Yaodexin Chemical;

[0121] F5606, ternary copolymer polypropylene, purchased from Yanshan Petrochemical;

[0122] Vistamaxx 6102, ethylene-propylene copolymer, purchased from Mobil.

[0123] I. Preparation of propylene-ethylene copolymer

[0124] Example 1

[0125] This embodiment provides a specific example of a method for preparing the propylene-ethylene copolymer of this application, including the following steps:

[0126] Propylene, ethylene, co-catalyst, and solvent are fed into a mixing tank with a propylene flow rate of 1700 g / h and an ethylene flow rate of 200 g / h. The co-catalyst is triisobutylaluminum, fed at an Al / M ratio of 200. The solvent is n-hexane, with a flow rate of 2660.4 g / h. The mixing tank has a volume of 2 L and a stirring speed of 200 r / min.

[0127] The mixed raw materials and catalyst were fed into the reactor separately, with the main catalyst being rac-ethylenebis(1-indenyl)zirconium dichloride, added at a rate of 20 μmol / h.

[0128] The reactor has a volume of 0.5L, a reaction temperature of 122℃, a reaction pressure of 4MPa, and a stirring speed of 600r / min; the polymerization reaction takes place in the reactor.

[0129] After the reaction was completed, the polymerization product and water vapor (flow rate 120 μmol / h) in the reactor were fed into a quenching vessel at a quenching temperature of 120℃ for 30 min. Then, the resulting material was fed into a flash devolatilization unit to remove n-hexane: the temperature of the first-stage devolatilization chamber was 200℃ and the devolatilization pressure was 0.05 MPa, and the temperature of the second-stage devolatilization chamber was 300℃ and the devolatilization pressure was -0.08 MPa, yielding a propylene / ethylene copolymer. The product properties are shown in Table 1.

[0130] Example 2

[0131] This embodiment provides a specific example of a method for preparing the propylene-ethylene copolymer of this application, including the following steps:

[0132] Propylene, ethylene, co-catalyst, and solvent are fed into a mixing tank, with a propylene flow rate of 1700 g / h and an ethylene flow rate of 200 g / h. The co-catalyst is triisobutylaluminum, fed at an Al / M ratio of 200. The solvent is n-hexane, with a flow rate of 2660.4 g / h. The mixing tank has a volume of 1 L and a stirring speed of 100 r / min.

[0133] The mixed raw materials and catalyst were fed into the reactor separately. The main catalyst was diphenylmethylenecyclopentadiene (2,7-di-tert-butyl-fluorenyl)zirconia dichloride, and the addition amount was 18 μmol / h.

[0134] The reactor has a volume of 0.5L, a reaction temperature of 122℃, a reaction pressure of 4MPa, and a stirring speed of 600r / min; the polymerization reaction takes place in the reactor.

[0135] After the reaction was completed, the polymerization product and water vapor (flow rate 120 μmol / h) in the reactor were fed into a quenching vessel at a quenching temperature of 120℃ for 30 min. Then, the resulting material was fed into a flash devolatilization unit to remove n-hexane: the temperature of the first-stage devolatilization chamber was 200℃ and the devolatilization pressure was 0.05 MPa, and the temperature of the second-stage devolatilization chamber was 300℃ and the devolatilization pressure was -0.08 MPa, yielding a propylene / ethylene copolymer. The product properties are shown in Table 1.

[0136] Example 3

[0137] This embodiment provides a specific example of a method for preparing the propylene-ethylene copolymer of this application, including the following steps:

[0138] Propylene, ethylene, co-catalyst, and solvent are fed into a mixing tank with a propylene flow rate of 1700 g / h and an ethylene flow rate of 200 g / h. The co-catalyst is triisobutylaluminum, fed at an Al / M ratio of 200. The solvent is Isopar-E, with a flow rate of 2660.4 g / h. The mixing tank has a volume of 5 L and a stirring speed of 400 r / min.

[0139] The mixed raw materials and catalyst were fed into the reactor separately, with the main catalyst being rac-ethylenebis(1-indenyl)zirconium dichloride, added at a rate of 20 μmol / h.

[0140] The reactor has a volume of 0.5L, a reaction temperature of 122℃, a reaction pressure of 4MPa, and a stirring speed of 600r / min; the polymerization reaction takes place in the reactor.

[0141] After the reaction was completed, the polymerization product and water vapor (flow rate 120 μmol / h) in the reactor were sent to a quenching vessel at a quenching temperature of 120℃ for 30 min. Then, the resulting material was sent to a flash devolatilization unit to remove Isopar-E: the temperature of the first-stage devolatilization chamber was 200℃ and the devolatilization pressure was 0.05 MPa, and the temperature of the second-stage devolatilization chamber was 300℃ and the devolatilization pressure was -0.08 MPa, to obtain a propylene / ethylene copolymer. The product properties are shown in Table 1.

[0142] Example 4

[0143] This embodiment provides a specific example of a method for preparing the propylene-ethylene copolymer of this application, including the following steps:

[0144] Propylene, ethylene, co-catalyst, and solvent are fed into a mixing tank with a propylene flow rate of 1700 g / h and an ethylene flow rate of 248 g / h. The co-catalyst is triisobutylaluminum, fed at an Al / M ratio of 200. The solvent is n-hexane, with a flow rate of 2660.4 g / h. The mixing tank has a volume of 2 L and a stirring speed of 200 r / min.

[0145] The mixed raw materials and catalyst were fed into the reactor separately. The main catalyst was diphenylmethylenecyclopentadiene (2,7-di-tert-butyl-fluorenyl)zirconia dichloride, and the addition amount was 18 μmol / h.

[0146] The reactor has a volume of 0.5L, a reaction temperature of 122℃, a reaction pressure of 4MPa, and a stirring speed of 600r / min; the polymerization reaction takes place in the reactor.

[0147] After the reaction was completed, the polymerization product and water vapor (flow rate 120 μmol / h) in the reactor were fed into a quenching vessel at a quenching temperature of 120℃ for 30 min. Then, the resulting material was fed into a flash devolatilization unit to remove n-hexane: the temperature of the first-stage devolatilization chamber was 200℃ and the devolatilization pressure was 0.05 MPa, and the temperature of the second-stage devolatilization chamber was 300℃ and the devolatilization pressure was -0.08 MPa, yielding a propylene / ethylene copolymer. The product properties are shown in Table 1.

[0148] Example 5

[0149] This embodiment provides a specific example of a method for preparing the propylene-ethylene copolymer of this application, including the following steps:

[0150] Propylene, ethylene, co-catalyst, and solvent are fed into a mixing tank, with a propylene flow rate of 1700 g / h and an ethylene flow rate of 160 g / h. The co-catalyst is triisobutylaluminum, fed at an Al / M ratio of 200. The solvent is n-hexane, with a flow rate of 2660.4 g / h. The mixing tank has a volume of 2 L and a stirring speed of 200 r / min.

[0151] The mixed raw materials and catalyst were fed into the reactor separately, with the main catalyst being bis(1,3-dimethylcyclopentadienyl)zirconia dichloride, added at a rate of 15 μmol / h.

[0152] The reactor has a volume of 0.5L, a reaction temperature of 122℃, a reaction pressure of 4MPa, and a stirring speed of 600r / min; the polymerization reaction takes place in the reactor.

[0153] After the reaction was completed, the polymerization product and water vapor (flow rate 120 μmol / h) in the reactor were fed into a quenching vessel at a quenching temperature of 120℃ for 30 min. Then, the resulting material was fed into a flash devolatilization unit to remove n-hexane: the temperature of the first-stage devolatilization chamber was 200℃ and the devolatilization pressure was 0.05 MPa, and the temperature of the second-stage devolatilization chamber was 300℃ and the devolatilization pressure was -0.08 MPa, yielding a propylene / ethylene copolymer. The product properties are shown in Table 1.

[0154] Comparative Example 1

[0155] The commercially available Vistamaxx 6102 was used.

[0156] Comparative Example 2

[0157] The propylene-ethylene copolymer was prepared using essentially the same method as in Example 1, except that the mixing tank volume was 0.5L.

[0158] Comparative Example 3

[0159] The propylene-ethylene copolymer was prepared using essentially the same method as in Example 1, except that the ethylene feed rate was 50 g / h.

[0160] Comparative Example 4

[0161] The propylene-ethylene copolymer was prepared using essentially the same method as in Example 1, except that the ethylene feed rate was 300 g / h.

[0162] Comparative Example 5

[0163] The propylene-ethylene copolymer was prepared using essentially the same method as in Example 1, except that the reaction temperature in the reactor was 66°C.

[0164] Comparative Example 6

[0165] The propylene-ethylene copolymer was prepared using essentially the same method as in Example 1, except that the reaction temperature in the reactor was 204°C.

[0166] Performance testing:

[0167] The performance of the propylene-ethylene copolymers in the above examples and comparative examples was tested using the following methods:

[0168] (1) Molecular weight, molecular weight distribution and ethylene insertion rate: GPC-IR test of polymer char, test temperature 150℃, product recovery rate is over 95%.

[0169] (2) Melting temperature (T) m The temperature was obtained by differential scanning calorimetry (DSC). The test procedure was as follows: the sample was heated to 210℃ and held for 5 minutes to eliminate thermal history. Then it was cooled to -60℃ and then heated to 210℃ again. The heating and cooling rate was 10℃ / min throughout the process. The melting temperature (Tm) was taken as the peak value of the melting point during the second heating process.

[0170] (3) Density: Measured by ASTM D792-2021 method.

[0171] (4) Nuclear magnetic resonance spectrometer: Bruker's AVANCE NEO 600MHz NMR SPECTROMETER. The sample was dissolved in deuterated dichlorobenzene at 120℃. During the high-temperature carbon NMR test, the test temperature was 120℃, with reverse gating decoupling, 3000 scans, and a pulse relaxation time of 10s.

[0172] Table 1. Performance test results of propylene-ethylene copolymers in the examples and comparative examples.

[0173] <![CDATA[M w (×10 4 )]]> PDI Ethylene insertion rate (wt%) <![CDATA[n1]]> <![CDATA[n2]]> γ <![CDATA[T m (℃)]]> Example 1 22.7 2.71 8.2 66.9 11 6.08 73.8 Example 2 22.6 2.51 8.5 67.8 10.3 6.58 78.4 Example 3 22.7 2.67 14.8 64.6 11.8 5.47 61.2 Example 4 20.6 2.49 10.2 61.2 11.1 5.51 67.5 Example 5 23.4 2.74 7.2 68.2 10.1 6.75 79.1 Comparative Example 1 24.5 2.48 13.7 48 13.9 3.45 105 Comparative Example 2 22.6 2.53 8.4 72.8 7.5 9.71 115.6 Comparative Example 3 25.8 2.37 6.2 80.3 7 11.47 123.5 Comparative Example 4 20.1 2.63 14.2 40.3 13.5 2.99 60.2 Comparative Example 5 36.7 2.34 5.7 74.5 6.4 11.64 130.2 Comparative Example 6 10.2 2.42 13.2 52.1 14.1 3.70 55.2

[0174] According to Table 1, the weight-average molecular weight (Mw) of the propylene-ethylene copolymer of this application is 15.0 × 10⁻⁶. 4 -25.0×10 4 Within this range, the n1 / n2 ratio (γ) is in the range of 5 to 7.5, and the melting temperature Tm is between 61.2℃ and 79.1℃. Comparative Example 1 used commercially available Vistamaxx 6102, with a γ value of only 3.45, resulting in a heat-sealing strength of 6.5 N, far lower than the 9.3 N of Example 1. Comparative Example 2 used a 0.5 L mixing tank, increasing the γ value to 9.71, leading to an increase in the initial sealing temperature to 109 °C. Comparative Example 3 had an ethylene feed rate of 50 g / h, increasing the γ value to 11.47, leading to an increase in the initial sealing temperature to 117 °C, almost identical to pure F5606 (118 °C), making low-temperature heat sealing impossible. Comparative Example 4 had an ethylene feed rate of 300 g / h, decreasing the γ value to 2.99, resulting in a heat-sealing strength of 4.2 N, severely deteriorating mechanical properties and failing to meet application requirements. Comparative Example 5 had a reaction temperature of 66 °C, insufficient catalyst activity, and an increase in weight-average molecular weight Mw to 36.7 × 10⁻⁶. 4 The γ value was as high as 11.64, and the melting temperature reached 130.2℃, resulting in an increased sealing temperature of 121℃. This excessively high sealing temperature made processing difficult and reduced practicality. Comparative Example 6 had a reaction temperature of 204℃, and the intense chain transfer and degradation resulted in a Mw of only 10.2 × 10⁻⁶. 4 The γ value is 3.70. The low molecular weight results in insufficient molecular chain entanglement, which leads to a heat seal strength of only 1.5N (see Table 2 for details).

[0175] II. Applications of propylene-ethylene copolymers

[0176] The propylene-ethylene copolymers of each embodiment and comparative example were prepared into cast films according to the following process:

[0177] The propylene-ethylene copolymer and the terpolymer polypropylene F5606 were blended at a mass ratio of 3:17, and a cast film was prepared using a single-layer casting machine (purchased from Guangdong Putong, model FDOU-22). The casting temperature was 190℃, and the thickness of the cast film was 50μm.

[0178] The performance of the cast film was tested using the following methods:

[0179] Mechanical performance testing shall be conducted in accordance with the national standard GB / T 27740-2011;

[0180] The heat sealing performance test shall be conducted in accordance with the national standard GB / T 27740-2011.

[0181] Table 2 Performance test results of cast films prepared from propylene-ethylene copolymers in the examples and comparative examples.

[0182] propylene / ethylene copolymer Tensile modulus (MPa) Elongation at break (%) Initial sealing temperature (°C) Heat seal strength (N) F5606 837 542 118 0.9 Example 1 536 588 89 9.3 Example 2 621 572 92 10.6 Example 3 501 611 81 8.8 Example 4 527 581 85 9 Example 5 584 577 90 9.8 Comparative Example 1 594 588 106 6.5 Comparative Example 2 674 525 109 11.3 Comparative Example 3 715 493 117 15.2 Comparative Example 4 424 658 81 4.2 Comparative Example 5 798 521 121 11.5 Comparative Example 6 364 431 92 1.5

[0183] As shown in Table 2, the propylene-ethylene copolymer of this application can effectively balance the initial sealing temperature and heat-sealing strength, enabling the polyolefin cast film to maintain high heat-sealing strength at a low initial sealing temperature while maintaining the mechanical properties of the film. Compared to Example 1, Comparative Example 1 used commercially available Vistamaxx 6102, whose initial sealing temperature was 106°C, significantly higher than 89°C in Example 1, and its heat-sealing strength was only 6.5N; Comparative Example 2 used a 0.5L mixing tank, resulting in uneven mixing, and its initial sealing temperature reached as high as 109°C, with a tensile modulus of 674MPa and an elongation at break of only 525%, indicating excessive film rigidity and decreased flexibility; Comparative Example 3 had an excessively low ethylene feed rate, resulting in an initial sealing temperature of 117°C, almost the same as pure F5606 (118°C), with a tensile modulus of 715MPa and an elongation at break of only 493%, indicating an excessively hard and brittle film; Example 4: Due to excessive ethylene feed rate, although the initial sealing temperature of its cast film was as low as 81℃, the heat seal strength was only 4.2N, the tensile modulus was only 424MPa, and the elongation at break was as high as 658%, indicating insufficient film strength. Comparative Example 5: The reaction temperature was too low, resulting in excessively high Mw. Its cast film had an initial sealing temperature as high as 121℃ and a tensile modulus as high as 798MPa (close to pure F5606). The film stiffness was too high and the flexibility was poor. Comparative Example 6: The reaction temperature was too high, resulting in excessively low Mw. Its cast film had a heat seal strength of only 1.5N, a tensile modulus of only 364MPa, and an elongation at break of only 431%, indicating poor mechanical properties. The above examples and comparative examples show that, under the synergistic effect of the weight-average molecular weight (150,000-250,000) and n1 / n2 ratio (5-7.5) specified in this application, propylene-ethylene copolymers can simultaneously achieve low initial sealing temperature (≤92℃), high heat seal strength (≥8.8N), and good mechanical properties (tensile modulus 500-650MPa, elongation at break ≥570%) in cast film applications, achieving a balance between low-temperature heat sealing and performance, and demonstrating significant application advantages.

[0184] The technical features of the above-described embodiments and examples can be combined in any suitable manner. For the sake of brevity, not all possible combinations of the technical features in the above-described embodiments and examples are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0185] The embodiments described above merely illustrate several implementation methods of this application and should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Furthermore, it should be understood that after reading the above teachings, those skilled in the art can make various alterations or modifications to this application, and the equivalent forms obtained also fall within the protection scope of this application. It should also be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the protection scope of the appended claims. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A propylene-ethylene copolymer, characterized in that, The monomers of the propylene-ethylene copolymer are ethylene and propylene, and the propylene-ethylene copolymer satisfies the following characteristics: (i) Weight-average molecular weight is 150,000-250,000; (ii) The molar percentage of propylene-propylene-propylene segments in the propylene-ethylene copolymer is n1, and the molar percentage of propylene-ethylene-propylene segments is n2, where 5 ≤ n1 / n2 ≤ 7.

5.

2. The propylene-ethylene copolymer according to claim 1, characterized in that, The propylene-ethylene copolymer satisfies one or more of the following characteristics: (iii) The melting temperature is 60℃-90℃; (iv) 60%≤n1≤75%; (v) 10% ≤ n2 ≤ 12%.

3. The propylene-ethylene copolymer according to claim 2, characterized in that, The propylene-ethylene copolymer satisfies one or more of the following characteristics: (vi) The density is 0.86 g / cm³ 3 -0.885g / cm 3 ; (vii) The polydispersity index is 2-4; (vii) The mass percentage of the ethylene chain segment is 1%-15%.

4. A method for preparing a propylene-ethylene copolymer, characterized in that, Includes the following steps: The preparation is carried out using a continuous reaction apparatus, which includes a mixing tank and a reaction tank connected together. Materials including propylene, ethylene, co-catalyst and solvent are continuously fed into a mixing tank and stirred at a first pressure and a first temperature. The material output from the mixing tank and the main catalyst are continuously fed into the reaction tank, and the reaction tank is stirred under a second pressure and a second temperature to obtain the propylene-ethylene copolymer. The ratio of the average residence time of the material in the mixing tank to the average residence time in the reaction tank is (2-6):1; The first pressure is 0.1-10 MPa, and the first temperature is 10℃-50℃; The second pressure is 1-10 MPa, and the second temperature is 70℃-200℃.

5. The preparation method according to claim 4, characterized in that, One or more of the following conditions must be met: (1) The volume ratio of the mixing tank to the reaction tank is (2-6):1; (2) The first pressure is 1MPa-5MPa, and the first temperature is 20℃-40℃; (3) The second pressure is 2MPa-6MPa and the second temperature is 80℃-170℃.

6. The preparation method according to claim 4 or 5, characterized in that, One or more of the following conditions must be met: (1) The length-to-diameter ratio of the mixing tank is (1-5):1; (2) The length-to-diameter ratio of the reaction vessel is (1-5):1; (3) The conditions for the first stirring include: the stirring speed is 100rpm-600rpm; (4) The conditions for the second stirring include: the stirring speed is 300 rpm to 800 rpm.

7. The preparation method according to claim 4 or 5, characterized in that, One or more of the following conditions must be met: (1) The main catalyst includes one or more of metallocene catalysts and non-metallocene catalysts; (2) The co-catalyst includes an aluminum additive, and optionally, also includes a boron additive; (3) The solvent includes one or more of alkane solvents, aromatic solvents, cycloalkanes solvents and haloalkanes solvents.

8. The preparation method according to claim 7, characterized in that, The metallocene catalyst comprises one or more of the following: rac-ethylene bis(1-indenyl)zirconia, racemic dimethylsilyl bis(1-indenyl)zirconia, diphenylmethylene(cyclopentadiene)(9-fluorenyl)zirconia, dimethyldimethylsilyl bis(2-methyl-4-phenyl-1-indenyl)zirconia, bis(methylcyclopentadiene)zirconia, bis(1,3-dimethylcyclopentadienyl)zirconia, dimethylsilylbis(2-methyl-4-phenylindenyl)zirconia, (cyclopentadienyl)(1,2-dimethoxyethane)zirconia trichloride, diphenylmethylenecyclopentadiene(2,7-di-tert-butyl-fluorenyl)zirconia, dimethylbis(propylcyclopentadienyl)hafnium, and bis(n-butylcyclopentadiene)hafnium; and / or, The non-metallocene catalyst includes one or more of the compounds shown in Formula I and Formula II; Formula I Formula II R1, R2, R6, and R7 are each independently selected from C1-C atoms that have undergone hydrogen or halogen substitution. 10 Alkyl, amino substituted C1-C 10 Alkyl or C1-C 10 alkyl; R3, R4, R5, R8, R9 and R 10 Each is independently selected from C1-C cells substituted with hydrogen or halogen. 10 Alkyl, amino substituted C1-C 10 Alkyl, C1-C 10 Alkyl or substituted or unsubstituted C6-C 10 Aryl; Q1 and Q2 are each independently selected from halogen-substituted C1-C 10 Alkyl, amino substituted C1-C 10 Alkyl, C1-C 10 Alkyl or halogen-substituted C6-C 10 Aryl and amino substituted C6-C 10 Aryl or C6-C 10 Aryl; Y is selected from carbon or silicon; X1 and X2 are each independently selected from halogenated, amino, or halogenated C1-C groups. 10 Alkyl, amino substituted C1-C 10 Alkyl or C1-C 10 alkyl; M is selected from group IVB metals.

9. The preparation method according to claim 4 or 5, characterized in that, One or more of the following conditions must be met: (1) The main catalyst accounts for 0.00001%-0.0009% of the mass of the material in the reaction vessel; (2) The co-catalyst includes an aluminum additive, and optionally, also includes a boron additive; (3) The amount of aluminum additive added is based on the molar ratio Al / M of metallic aluminum and metallic M in the main catalyst, where Al / M is 1-3000; (4) The amount of boron additive added is based on the molar ratio of boron element to metal M in the main catalyst, B / M, where B / M is 0-10; (5) The mass ratio of propylene to solvent is (0.2-0.9):1; (6) The mass percentage of ethylene is 3%-20% based on the total mass of ethylene and propylene being 100%.

10. The use of the propylene-ethylene copolymer according to any one of claims 1-3 or the propylene-ethylene copolymer prepared by the preparation method according to any one of claims 4-9 in the preparation of heat-sealing materials.

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