Olefin polymer and preparation method therefor

Abstract

The present invention relates to the field of olefin polymerization. Disclosed are an olefin polymer and a preparation method therefor. The olefin polymer comprises: a component (i): a fraction of the olefin polymer obtained by temperature-rising elution fractionation at an elution temperature higher than 140°C; a component (ii): a fraction of the olefin polymer obtained by temperature-rising elution fractionation at an elution temperature greater than 100°C and not higher than 140°C; a component (iii): a fraction of the olefin polymer obtained by temperature-rising elution fractionation at an elution temperature higher than 50°C and not higher than 100°C; and a component (iv): a fraction of the olefin polymer obtained by temperature-rising elution fractionation at an elution temperature higher than 0°C and not higher than 50°C, wherein the component (i) accounts for 20-80 wt%, the component (ii) accounts for 2-30 wt%, the component (iii) accounts for 5-30 wt%, and the component (iv) accounts for 10-50 wt%. The olefin polymer has more excellent flexural modulus and izod impact strength.

Description

Olefin polymer and method for producing the same

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Chinese Patent Application No. 202410990099.8, filed July 23, 2024, the contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of olefin polymers, in particular to an olefin polymer and a method for producing the same. BACKGROUND

[0004] Heterophasic polypropylene generally has two phases (island-in-sea structure) consisting of a polypropylene matrix and a distributed elastomer phase, or there can also be a three-phase structure (core-shell-matrix structure) consisting of a polypropylene matrix and a distributed elastomer phase, but the elastomer phase is wrapped with other semi-crystalline polymers. In the existing polymerization process of heterophasic copolymerized polypropylene, the typical method is to produce in two reaction stages in series. First, isotactic polypropylene (iPP) particles are produced in gaseous or liquid propylene. These polypropylene particles are then transferred to a gas-phase fluidized bed reactor to copolymerize to produce an elastomer rubber phase within the isotactic polypropylene matrix. The elastomer phase contains propylene copolymer rubber, such as ethylene-propylene rubber (EPR). The rubber component is thus a copolymer of propylene and another alpha-olefin (such as ethylene), and is mainly amorphous (xylene room temperature soluble) in form.

[0005] Heterophasic propylene copolymers can be applied in many fields due to their good impact toughness and flowability, such as the exterior and interior of automobiles, especially instrument panels, door cladding, consoles, trim, etc., and in packaging fields such as food packaging, medical packaging, and consumer goods, etc.

[0006] The gas-phase copolymerization reactor has limited heat removal capacity due to the small heat capacity of the ethylene and propylene reaction medium. Although the heat of polymerization of ethylene-propylene copolymer is about 33% lower than that of ethylene polymerization, the ethylene-propylene amorphous rubber is more prone to melt under heat, and poor heat transfer control can cause the product to stick together, impairing the flowability of the particles, and in severe cases even causing the reactor to be stuck and shut down. Therefore, good control of the gas-phase copolymerization reaction temperature and effective strengthening of the heat transfer capacity are very important.

[0007] In the conventional propylene polymerization process, a typical method is to use the Unipol polypropylene process, which is a kind of gas phase fluidized bed polypropylene process. Although the conventional Unipol polypropylene process has simple process flow, less equipment, high safety and reliability of device production, and high economy of device operation, the production capacity is limited by the reaction heat in the fluidized bed, and the produced product structure is relatively simple, single function, and lacks relatively high performance value-added. US4588790 discloses a process for producing polymers by operating in a gas phase fluidized bed condensation mode, which introduces a condensable liquid, i.e. a condensing medium (generally a copolymerized higher alpha-olefin or an inert saturated hydrocarbon), which evaporates in the fluidized bed reactor to enhance the removal of polymerization heat, thereby doubling the space-time yield of the fluidized bed reactor.

[0008] CN105732849A discloses an olefin polymerization device and method, which realizes the switching of olefin copolymerization and homopolymerization, copolymerization and copolymerization by intermittently introducing a condensing agent and / or a comonomer to the side wall of the reactor. This method has the problems of long switching time of the polymerization environment and the inability to achieve micro-level mixing of the polymerization products. SUMMARY

[0009] The purpose of the present application is to overcome the problem that the olefin polymer in the prior art cannot have high bending modulus and high cantilever beam impact strength, and to provide an olefin polymer and a preparation method thereof. The olefin polymer includes four components with specific compositions and contents, which cooperate with each other to avoid the phase separation defect easily generated in traditional physical mixing, while retaining the excellent processing performance of the olefin polymer, so that the olefin polymer has more excellent bending modulus and cantilever beam impact strength.

[0010] To achieve the above purpose, the first aspect of the present application provides an olefin polymer, wherein the olefin polymer comprises the following four components:

[0011] Component (i): a fraction with a temperature of greater than 140℃ obtained by temperature rising elution fractionation of the olefin polymer;

[0012] Component (ii): a fraction with a temperature of greater than 100℃ and not higher than 140℃ obtained by temperature rising elution fractionation of the olefin polymer;

[0013] Component (iii): a fraction with a temperature of greater than 50℃ and not higher than 100℃ obtained by temperature rising elution fractionation of the olefin polymer;

[0014] Component (iv): a fraction with a temperature of greater than 0℃ and not higher than 50℃ obtained by temperature rising elution fractionation of the olefin polymer;

[0015] The content of component (i) is 20-80 wt%, the content of component (ii) is 2-30 wt%, the content of component (iii) is 5-30 wt%, and the content of component (iv) is 10-50 wt%.

[0016] The second aspect of the present application provides a method for preparing an olefin polymer, comprising the following steps:

[0017] (1) polymerizing the polymer and an olefin monomer in the presence of a catalyst to obtain an olefin polymer;

[0018] (2) discharging the gas not involved in the reaction and not completely reacted in step (1) to obtain a circulating gas;

[0019] (3) compressing and / or cooling the circulating gas to obtain a gas-liquid mixture;

[0020] (4) separating the gas-liquid mixture to obtain a heavy component stream and a light component stream;

[0021] (5) returning the heavy component stream and the light component stream to step (1) respectively;

[0022] The olefin monomer comprises propylene, ethylene and optionally an alpha-olefin.

[0023] The separation factor of the heavy component stream and the light component stream is more than 80%, and the volume flow rate of the light component stream returned to step (1) is 5-80 times the volume flow rate of the heavy component stream returned to step (1).

[0024] The third aspect of the present application provides an olefin polymer prepared by the above preparation method.

[0025] Through the above technical solution, the olefin polymer and the preparation method thereof provided by the present application have the following beneficial effects:

[0026] (1) The olefin polymer provided by the present application comprises four components with specific compositions and contents, and the cooperation of each component can avoid the phase separation defect easily generated in traditional physical mixing, while retaining the excellent processing performance of the olefin polymer, so that the olefin polymer has more excellent flexural modulus and Izod impact strength.

[0027] (2) In the present application, the method makes four polymerization regions exist in the polymerization reactor at the same time, and by controlling the separation factor of the heavy component stream and the light component stream, the volume flow rate of the heavy component stream returned to step (1), and the volume flow rate of the light component stream returned to step (1), the size of each region can be effectively changed, so as to change the content of each structure in the polymer, and finally realize the improvement of the mechanical properties of the polymer.

[0028] (3) In the present application, the method further narrows down the value range of parameters such as the separation factor of the heavy component stream and the light component stream, the volume flow rate of the heavy component stream returned to step (1), and the volume flow rate of the light component stream returned to step (1), thereby better controlling the content of each structure in the polymer, so that the mechanical properties of the polymer, especially the Izod impact strength at low temperature, are further improved.

[0029] (4) In the present application, the method reduces the temperature in the polymerization reactor by discharging the high-temperature gas in the polymerization reactor and introducing the gas phase and the liquid phase with lower temperature; in addition, the propylene in the liquid phase will become gaseous after entering the polymerization reactor, and in this process, the propylene further absorbs the heat in the polymerization reactor, finally improving the heat removal capacity of the reaction system.

[0030] (5) In the present application, the system introduces the gas phase from the bottom and the liquid phase from the side wall symmetrically, thereby better controlling the size of each region in the reactor, so as to better achieve the control of the polymer structure and the improvement of the mechanical properties. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a schematic diagram of the system used in the method of the second aspect of the present application.

[0032] Figure 2 is the phase morphology and copolymer composition distribution of the polymer obtained by AFM-IR characterization.

[0033] BRIEF DESCRIPTION OF DRAWINGS 1 polymerization reactor; 2 compressor; 3 heat exchanger; 4 separation device. DETAILED DESCRIPTION

[0034] The first aspect of the present application provides an olefin polymer, wherein the olefin polymer comprises the following four components:

[0035] Component (i): a fraction with a temperature of greater than 140℃ obtained by temperature rising elution fractionation of the olefin polymer;

[0036] Component (ii): a fraction with a temperature of greater than 100℃ and not higher than 140℃ obtained by temperature rising elution fractionation of the olefin polymer;

[0037] Component (iii): a fraction with a temperature of greater than 50℃ and not higher than 100℃ obtained by temperature rising elution fractionation of the olefin polymer;

[0038] Component (iv): a fraction with a temperature of greater than 0℃ and not higher than 50℃ obtained by temperature rising elution fractionation of the olefin polymer;

[0039] The content of component (i) is 20-80wt%, the content of component (ii) is 2-30wt%, the content of component (iii) is 5-30wt%, and the content of component (iv) is 10-50wt%.

[0040] In the present application, the olefin polymer comprises the four components with the above specific compositions and contents, wherein the existence of component (ii) and component (iii) can form a uniformly dispersed random distribution segment structure or a micro-phase separation block structure in the polyolefin molecular chain, wherein the component (ii) with the random distribution segment structure can destroy the regularity of the polyolefin polymer crystallization, improve the transparency and low-temperature flexibility of the polymer, and the component (iii) with the micro-phase separation block structure can greatly improve the impact resistance by using the energy dissipation mechanism, and the cooperation of the components can avoid the phase separation defects easily generated in the traditional physical mixing, while retaining the excellent processing performance of the olefin polymer, so that the olefin polymer has more excellent flexural modulus and cantilever beam impact strength.

[0041] In the present application, the sum of the contents of component (i), component (ii), component (iii) and component (iv) is 100wt%.

[0042] In the present application, the four components are obtained by temperature rising elution fractionation of the olefin polymer.

[0043] In the present application, the test conditions of the temperature rising elution fractionation include: firstly, about 2.0g of the sample and 0.1wt% of the antioxidant (2,6-di-tert-butyl-4-methylphenol) are fully dissolved in 250mL of boiling xylene. Then the polymer hot solution is transferred to a glass column filled with quartz sand with a pore size of 250-380μm (40-60 mesh), and the temperature in the glass column is constant at 140℃. Then the glass column is cooled to 30℃ at a cooling rate of 1.5℃ / h, and the polymer in the solution is slowly crystallized. In the gradient temperature rising elution step, the glass column is kept at a set temperature for more than 3h to ensure that the crystallizable polymer reaches the dissolution equilibrium. Then, at least 400mL of xylene hot solvent at the set temperature is used to slowly elute the dissolved polymer in the glass column, and the collected eluate is numbered. Finally, a rotary evaporator is used to spin-evaporate the xylene solution to only a small amount of solvent, and isopropanol is added for back extraction. The mixture solution is filtered, and the solid is dried in a vacuum oven at 60℃ to obtain the fractions corresponding to different elution temperatures.

[0044] In the present application, the main component of component (i) is a polypropylene segment; the main component of component (ii) is a polyethylene segment; the main component of component (iii) is a block copolymer phase; and the main component of component (iv) is a rubber phase.

[0045] According to a particularly preferred embodiment of the present application, each of the component (iii) and the component (iv) independently comprises at least two of an ethylene segment, a propylene segment and an alpha-olefin segment.

[0046] In the present application, "polypropylene segment" refers to a segment structure formed by ≥ 50 consecutive propylene units; "propylene segment" refers to a segment structure formed by ≥ 5 consecutive propylene units; "polyethylene segment" refers to a segment structure formed by 50 consecutive ethylene units; "ethylene segment" refers to a segment structure formed by ≥ 5 consecutive ethylene units; and "alpha-olefin segment" refers to a segment structure formed by ≥ 5 consecutive alpha-olefin units.

[0047] In the present application, "alpha-olefin" refers to an olefin having a carbon atom number of ≥ 4.

[0048] According to a particularly preferred embodiment of the present application, the carbon atom number of the alpha-olefin is ≤ 18, and more preferably butene and / or 1-hexene. The use of the alpha-olefin within the above preferred range can result in a polymer having more excellent properties.

[0049] To further improve the flexural modulus and Charpy impact strength of the olefin polymer, preferably, the content of component (i) is 20-80 wt%, for example, can be 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, 50 wt%, 52 wt%, 54 wt%, 56 wt%, 58 wt%, 60 wt%, 62 wt%, 64 wt%, 66 wt%, 68 wt%, 70 wt%, 72 wt%, 74 wt%, 76 wt%, 78 wt%, 80 wt%, and the range consisting of any two values, preferably 40-60 wt%; the content of component (ii) is 2-30 wt%, for example, can be 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, and the range consisting of any two values, preferably 3-20 wt%; the content of component (iii) is 5-30 wt%, for example, can be 5 wt%, 7 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, and the range consisting of any two values, preferably 5.3-20 wt%; the content of component (iv) is 10-50 wt%, for example, can be 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, 50 wt%, and the range consisting of any two values, preferably 30-45 wt%.

[0050] According to a particularly preferred embodiment of the present application, the content of ethylene segments in component (iii) is 20-30 wt%;

[0051] and / or, the content of ethylene segments in component (iv) is 30-50 wt%.

[0052] In the present application, "ethylene segments" refer to segment structures formed by ≥5 consecutive ethylene units.

[0053] In the present application, when the content of ethylene segments in component (iii) and / or component (iv) satisfies the above range, the ethylene segments (usually ≥5 continuous ethylene units) form nanometer-scale "soft phase" (ethylene-propylene rubber phase, EPR) due to the difference in compatibility with propylene segments, which is dispersed in the "hard phase" matrix mainly composed of polypropylene segments, forming "island" or "co-continuous" morphology, so that the flexural modulus and the Charpy impact strength of the olefin polymer are further improved or improved.

[0054] In the present application, the content of ethylene segments in component (iii) and component (iv) is measured by nuclear magnetic resonance (NMR) method. Specifically, the sequence distribution of the polymerization product is measured according to the following method 13 C NMR measurement, the instrument used is Mercury Plus 300 nuclear magnetic resonance spectrometer produced by Varian Company of USA. 50-80 mg of the sample to be measured is added to the nuclear magnetic tube, deuterated o-dichlorobenzene is selected as the solvent, and the sample is prepared at a concentration of 10 W / V%. The test conditions are set as follows: the temperature is 120°C, the resolution is 400MHz, the sampling time is 0.8s, the relaxation time is 3s, and the scanning number is 5000 times.

[0055] In order to further improve the flexural modulus and the Charpy impact strength of the olefin polymer, preferably, the content of ethylene segments in component (iii) is 20-30wt%, for example, it can be 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt%, and a range composed of any two values, preferably 25-30wt%; the content of ethylene segments in component (iv) is 30-50wt%, for example, it can be 30wt%, 32wt%, 34wt%, 36wt%, 38wt%, 40wt%, 42wt%, 44wt%, 46wt%, 48wt%, 50wt%, and a range composed of any two values, preferably 30-40wt%.

[0056] As mentioned before, in the present application, the main component of component (i) is polypropylene segment, but in the present application, component (i) can also include a small amount of ethylene segments, as long as the content of ethylene segments in component (i) is less than 1wt%, for example, the content of ethylene segments in component (i) is 0.9wt%, 0.8wt%, 0.7wt%, 0.6wt%, 0.5wt%, 0.4wt%, 0.3wt%, 0.2wt%, 0.1wt%, or 0wt%.

[0057] As mentioned above, in the present application, the main component of component (ii) is polyethylene segment, but in the present application, component (ii) can also contain other segments in addition to the ethylene segment, as long as the content of the ethylene segment in component (ii) is greater than 95 wt%, for example, the content of the ethylene segment in component (ii) is 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, 99.1 wt%, 99.2 wt%, 99.3 wt%, 99.4 wt%, 99.5 wt%, 99.6 wt%, 99.7 wt%, 99.8 wt%, 99.9 wt%, or 100 wt%.

[0058] According to a particularly preferred embodiment of the present application, the weight average molecular weight (Mw) of the olefin polymer is 5 x 10 4 g / mol-55 x 10 4 g / mol, the number average molecular weight (Mn) is 3 x 10 4 g / mol-15 x 10 4 g / mol; and the molecular weight distribution is 3-8.

[0059] In the present application, when the weight average molecular weight, the number average molecular weight and the molecular weight distribution of the olefin polymer meet the above ranges, the olefin polymer exhibits a unique "rigidity-toughness balance" property, in which a higher weight average molecular weight imparts excellent mechanical strength and melt strength through molecular chain entanglement, and a moderate number average molecular weight ensures good processing fluidity; at the same time, a wider molecular weight distribution makes short segments improve processing performance and long segments maintain mechanical performance, thereby achieving a synergistic optimization of high strength, high impact resistance and good processability.

[0060] In the present application, the weight average molecular weight, the number average molecular weight and the molecular weight distribution of the olefin polymer are measured by a high temperature gel permeation chromatography (GPC) method, and in a specific embodiment of the present application, the weight average molecular weight, the number average molecular weight and the molecular weight distribution of the olefin polymer are measured according to the following method: the molecular weight and its distribution are measured by a high temperature gel permeation chromatography system of PL GPC 220 type of Polymer Laboratories, UK, which is equipped with a differential refractive index detector. Before testing, a narrow distribution polystyrene standard sample is used for instrument calibration. 1,2,4-trichlorobenzene (TCB) is used as the mobile phase, the flow rate is set to 1.0 mL / min, and 0.0125 wt% of 2,6-di-tert-butyl-4-methylphenol is added as a stabilizer. The sample to be tested is continuously dissolved in TCB solvent at 160°C for 4-6 hours to ensure complete dissolution before testing.

[0061] In order to further improve the strength, impact resistance and processability of the olefin polymer, preferably, the weight average molecular weight of the olefin polymer is 5 x 10 4g / mol - 55 × 10 4 g / mol, for example, can be 5 × 10 4 g / mol, 10×10 4 g / mol, 15×10 4 g / mol, 20×10 4 g / mol, 25×10 4 g / mol, 30×10 4 g / mol, 35×10 4 g / mol, 40×10 4 g / mol, 45×10 4 g / mol, 50×10 4 g / mol, 55×10 4 g / mol, and a range consisting of any two values, preferably 20 × 10⁻⁶. 4 g / mol - 45 × 10 4 g / mol; preferably, the number-average molecular weight of the olefin polymer is 3 × 10⁻⁶ g / mol. 4 g / mol⁻¹⁵×10⁻¹⁰ 4 g / mol, for example, could be 3 × 10⁻⁶ g / mol. 4 g / mol, 5×10 4 g / mol, 7×10 4 g / mol, 9×10 4 g / mol, 11×10 4 g / mol, 13×10 4 g / mol, 15×10 4 g / mol, and the range of any two values, preferably 4 × 10⁻⁶. 4 g / mol-10×10 4 g / mol; preferably, the molecular weight distribution of the olefin polymer is 3-8, for example, it can be 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, 5.2, 5.4, 5.6, 5.8, 6, 6.2, 6.4, 6.6, 6.8, 7, 7.2, 7.4, 7.6, 7.8, 8, and any range between two values, preferably 6-7.

[0062] According to a particularly preferred embodiment of the present invention,

[0063] The crystallinity of component (iii) is 20-30%;

[0064] And / or, the crystallinity of component (iv) is less than 1%.

[0065] In the present application, when the crystallinity of component (iii) and / or component (iv) in the olefin polymer satisfies the above range, component (iv) is completely in amorphous state, thereby endowing the material with excellent elasticity and low temperature performance; component (iii) contains partially crystalline regions, which can serve as physical crosslinking points to significantly improve the mechanical strength and processing stability of the material. There is a synergistic effect between the micro-phase separation structure formed due to the difference in crystallinity between component (iii) and component (iv), the amorphous component (iii) (i.e. ethylene-propylene rubber phase EPR) provides flexibility and toughness, and the component (iv) with moderate crystallinity maintains the rigidity of the molecular chain of the olefin polymer, and the two components synergistically cooperate to make the olefin polymer have both high elasticity and processability.

[0066] In the present application, the crystallinity of each component is measured by differential scanning calorimetry (DSC) method. Specifically, the fractions obtained by temperature rising elution fractionation are tested by differential scanning calorimetry, and the DSC program is set as follows: the initial temperature is set to 30℃, first heated at a rate of 10℃ / min, the temperature is raised to 200℃ and stopped, and kept for 5min. The purpose of this heating operation is to eliminate the thermal history of the polymer. Then, the temperature is lowered at a rate of 10℃ / min to 30℃ and stopped, and kept for 1min, and then heated to 200℃ at the same heating rate.

[0067] In order to further improve the elasticity and processability of the olefin polymer, preferably, the crystallinity of component (iii) is 20-30%, for example, 20%, 22%, 24%, 26%, 28%, 30%, and any range consisting of two values, preferably 23-30%; the crystallinity of component (iv) is less than 1%, for example, it can be 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, preferably 0%.

[0068] In the present application, the crystallinity of component (i) is not particularly required and can be selected according to actual needs, for example, the crystallinity of component (i) is 20-65%, for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, more preferably 30-60%.

[0069] In the present application, the crystallinity of component (ii) is not particularly required and can be selected according to actual needs, for example, the crystallinity of component (ii) is 5-50%, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, more preferably 6-40%.

[0070] According to a particularly preferred embodiment of the present application, the olefin polymer comprises a continuous phase, and a dispersed phase dispersed in the continuous phase, and a first interface formed by the dispersed phase and the continuous phase;

[0071] The continuous phase comprises component (i);

[0072] The dispersed phase comprises a core mainly composed of component (ii), and a shell layer mainly composed of component (iv);

[0073] The first interface comprises component (iii).

[0074] In the present application, the olefin polymer has the above specific structure, and each component is distributed in the olefin polymer in the above specific manner, which can greatly improve the interfacial adhesion between the polypropylene matrix and the rubber phase, and the ethylene segments can co-crystallize with the polyethylene core of the core-shell particle, so that the interfacial interaction between the polyethylene core and the rubber phase is stronger, achieving the synergistic effect of enhanced multi-phase interfacial interaction and improved compatibility, and finally making the olefin polymer have excellent flexural modulus and Charpy impact strength.

[0075] According to a particularly preferred embodiment of the present application, the crystallinity at the first interface is 20-65%;

[0076] And / or, the crystallinity at the second interface formed by the core and the shell layer in the dispersed phase is 5-50%.

[0077] In the present application, the inventors have found that the crystallinity at the first interface formed by the dispersed phase and the continuous phase is close to the crystallinity of component (i), so the crystallinity of component (i) is used instead of the crystallinity at the first interface; and the crystallinity at the second interface formed by the core and the shell layer in the dispersed phase is close to the crystallinity of component (ii), so the crystallinity of component (ii) is used instead of the crystallinity at the second interface.

[0078] The second aspect of the present application provides a method for preparing an olefin polymer, which comprises the following steps:

[0079] (1) polymerizing the polymer and the olefin monomer in the presence of a catalyst to obtain an olefin polymer;

[0080] (2) discharging the gas not involved in the reaction and not completely reacted in step (1) to obtain a circulating gas;

[0081] (3) compressing and / or cooling the circulating gas to obtain a gas-liquid mixture;

[0082] (4) separating the gas-liquid mixture to obtain a heavy component stream and a light component stream;

[0083] (5) returning the heavy component stream and the light component stream to step (1) respectively;

[0084] wherein the olefin monomers comprise propylene, ethylene and optionally alpha-olefins;

[0085] wherein the separation factor of the heavy component stream and the light component stream is above 80%; the volume flow rate of the light component stream returned to step (1) is 5-80 times of the volume flow rate of the heavy component stream returned to step (1).

[0086] The preparation method of the olefin polymer provided by the application in-situ copolymerizes the olefins in one polymerization reactor, the synthesized copolymer has more uniform chain segment distribution and more stable phase morphology, can effectively improve the transparency and flexibility, significantly improve the impact resistance and improve the interaction between the molecular chains to enhance the mechanical strength, meanwhile, the phase separation problem caused by physical blending can be avoided, thereby the olefin copolymer with excellent mechanical properties is prepared.

[0087] In the application, the heavy component stream is in liquid phase and the light component stream is in gas phase if not otherwise specified.

[0088] In the application, the alpha-olefin is an olefin with carbon atom number greater than or equal to 4 if not otherwise specified.

[0089] In the application, the separation factor refers to the separation degree of the light and heavy key components (ethylene or propylene), which can be described by the following formula:

[0090] wherein S is the separation factor, x l is the molar fraction of the light key component (ethylene), x h is the molar fraction of the heavy key component (propylene), and D represents the top of the separation device and W represents the bottom of the separation device.

[0091] In the application, the compression, cooling and separation of the circulating gas are combined with the return of the heavy component stream and the light component stream. By controlling the separation factor of the separated heavy component stream and the light component stream, the composition and volume flow rate of the heavy component stream and the light component stream are affected, and then the size of each reaction region in the polymerization reactor is affected, so that the prepared polymer has excellent mechanical properties.

[0092] According to a particularly preferred embodiment of the application, in step (1), the polymer is a propylene polymer. The propylene polymer can be a propylene homopolymer and / or a propylene copolymer.

[0093] According to a particularly preferred embodiment of the present application, the weight average molecular weight of the propylene homopolymer is 100000-800000 g / mol, and the weight average molecular weight of the propylene copolymer is 100000-500000 g / mol.

[0094] In the present application, the type of the propylene copolymer can be selected from a wide range, and a person skilled in the art can select it according to actual needs. For example, the propylene copolymer is a propylene ethylene copolymer and / or a propylene alpha-olefin copolymer. More preferably, the content of propylene in the propylene copolymer is 80-98 wt%.

[0095] In the present application, the amount of the polymer can be selected from a wide range, and a person skilled in the art can select it according to actual needs. For example, the amount of the polymer is 0.001-0.99 t / tPP. Here, t / tPP refers to the mass of the polymer relative to one ton of olefin.

[0096] According to a particularly preferred embodiment of the present application, in step (4), the separation factor of the heavy component stream and the light component stream is 80-98%, more preferably 85-98%. By using the separation factor in the above more preferred range, the ethylene and propylene in the system can be better separated, so that the unreacted gas in the system can be fully utilized.

[0097] In the present application, the volume flow rate of the heavy component stream or the light component stream returned to step (1) is not particularly limited, as long as the return of the heavy component stream or the light component stream can be achieved, and a person skilled in the art can select it according to actual needs. For example, the volume flow rate of the heavy component stream or the light component stream returned to step (1) varies with the size of the polymerization reactor. Taking the fluidized bed reactor used in the examples of the present application as an example, the volume flow rate of the heavy component stream returned to step (1) is 1.5-4 m 3 / h.

[0098] According to a particularly preferred embodiment of the present application, in step (5), the volume flow rate of the light component stream returned to step (1) is 10-70 times the volume flow rate of the heavy component stream returned to step (1).

[0099] According to a particularly preferred embodiment of the present application, in step (5), the heavy component stream includes propylene, ethylene and optional alpha-olefins.

[0100] According to a particularly preferred embodiment of the present application, in step (5), the molar fraction of propylene in the heavy component stream is 60-99%, preferably 65-95%, more preferably 80-95%, based on the total molar amount of propylene, ethylene and optional alpha-olefins. By using the molar fraction of propylene in the above preferred range, multiple reaction environments can be better constructed in the reactor.

[0101] According to a particularly preferred embodiment of the present application, in step (5), the light component stream comprises ethylene and propylene. In the present application, the light component stream comprises optional modifiers and / or protective gases.

[0102] According to a particularly preferred embodiment of the present application, in step (5), the mole fraction of ethylene in the light component stream is 60-99%, preferably 65-95%, more preferably 80-95%, based on the total moles of propylene and ethylene. The use of the above preferred range of mole fraction of propylene can better build multiple reaction environments in the reactor.

[0103] According to a particularly preferred embodiment of the present application, the number of carbon atoms of the α-olefin is less than or equal to 18, more preferably butene and / or 1-hexene. The use of the above preferred range of α-olefin can make the prepared polymer have more excellent performance.

[0104] According to a particularly preferred embodiment of the present application, in step (1), the volume flow rates of the olefin monomer, the heavy component stream, and the light component stream are such that the mole fraction of ethylene is 15-40%, the mole fraction of propylene is 55-80%, and the mole fraction of α-olefin is 0-5%, based on the total moles of ethylene, propylene, and α-olefin; more preferably, the mole fraction of ethylene is 20-36%, the mole fraction of propylene is 61-78%, and the mole fraction of α-olefin is 0-3%. The use of the above preferred range of mole fraction can make the prepared polymer have more excellent performance.

[0105] According to a particularly preferred embodiment of the present application, in step (1), the polymerization reaction is carried out in the presence of a modifier. The modifier can further adjust the molecular weight of the polymerization product, so that the prepared polymer has more excellent performance.

[0106] In the present application, the use of the modifier is a common technical means in the art, and the selection range of the type and amount of the modifier is wide, and the person skilled in the art can select according to the actual needs. Preferably, the modifier comprises hydrogen; further preferably, the mole ratio of the modifier to propylene is 0.01-0.5:1, for example, it can be a specific ratio of 0.01:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, or a range between any two of them, more preferably 0.05-0.15:1. The use of the above preferred range of mole ratio of the modifier to propylene can make the prepared polymer have more excellent mechanical properties.

[0107] According to a particularly preferred embodiment of the present application, in step (1), the polymerization reaction is carried out in the presence of a protective gas. In the present application, the use of a protective gas is a common technical means in the art, and the selection range of the type and amount of the protective gas is wide, and the person skilled in the art can select according to the actual needs. Preferably, the protective gas is nitrogen.

[0108] According to a particularly preferred embodiment of the present application, the pressure of the polymerization reaction is 0.5-5 MPa (for example, it can be a specific pressure of 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 MPa, or a range between any two of them), and the temperature of the polymerization reaction is 50-100℃ (for example, it can be a specific temperature of 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100℃, or a range between any two of them).

[0109] According to a particularly preferred embodiment of the present application, the pressure of the polymerization reaction is regulated by introducing a mixed gas.

[0110] In the present application, the type of mixed gas is selected in a wide range, and the person skilled in the art can select according to the actual needs. Preferably, the mixed gas contains ethylene and propylene.

[0111] In the present application, in step (1), the type of catalyst is selected in a wide range, and the person skilled in the art can select according to the actual needs. Preferably, the catalyst is selected from a Ziegler-Natta type catalyst and / or a metallocene catalyst, and more preferably a Ziegler-Natta type catalyst.

[0112] In the present application, in step (1), the amount of catalyst is selected in a wide range, and the person skilled in the art can select according to the actual needs. Preferably, the amount of catalyst is 5-500 g / tPP. Wherein, g / tPP refers to the mass of catalyst relative to one ton of olefin.

[0113] According to a particularly preferred embodiment of the present application, the Ziegler-Natta type catalyst comprises a cocatalyst and an external electron donor as a stereoregulator.

[0114] In the present application, the selection range of the reaction vessel for the polymerization reaction is wide, and the person skilled in the art can select according to the actual needs. Preferably, the polymerization reaction is carried out in a fluidized bed reactor.

[0115] In the present application, the source of the polymer in step (1) is not particularly limited, and it can be purchased or prepared according to the following steps:

[0116] The propylene and optionally the comonomer are pre-polymerized to obtain the polymer.

[0117] According to a particularly preferred embodiment of the present application, in step (1), the polymer is obtained by pre-polymerization of propylene.

[0118] According to a particularly preferred embodiment of the present application, a regulator is present during the pre-polymerization process.

[0119] According to a particularly preferred embodiment of the present application, the pre-polymerization is carried out at a temperature of 20-50°C and a pressure of 0.04-0.8 MPa; more preferably, the pre-polymerization is carried out at a temperature of 25-35°C and a pressure of 0.1-0.6 MPa.

[0120] According to a particularly preferred embodiment of the present application, in step (3), the compression is carried out by a compressor.

[0121] According to a particularly preferred embodiment of the present application, in step (3), the cooling is carried out by a heat exchanger.

[0122] According to a particularly preferred embodiment of the present application, in step (3), the circulating gas is compressed to a pressure of 0.01-1 MPa. By taking a pressure within the above-mentioned preferred range, the propylene can be more effectively converted into liquid state while keeping the ethylene in gaseous state.

[0123] According to a particularly preferred embodiment of the present application, in step (3), the circulating gas is cooled to a temperature of 5°C-60°C, preferably 20-60°C, more preferably 25-40°C. By taking a temperature within the above-mentioned preferred range, the propylene can be more effectively converted into liquid state while keeping the ethylene in gaseous state.

[0124] According to a particularly preferred embodiment of the present application, in step (3), the molar fraction of the gas phase is 50-90% based on the total moles of the gas-liquid mixture. For example, the molar fraction can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or a range between any two of the above-mentioned values.

[0125] According to a particularly preferred embodiment of the present application, in step (4), the separation is carried out by a separation device. The selection of the separation device is wide in the present application, as long as it can achieve the separation of gas and liquid, and the person skilled in the art can select according to the actual needs. For example, the separation device can be a fractionating column.

[0126] According to a particularly preferred embodiment of the present application, in step (4), the separation temperature is 20-60°C, more preferably 35-58°C; and the separation pressure is 1-3 MPa, more preferably 1.5-2.5 MPa. By adopting the parameters within the above ranges, the separation factor can be effectively controlled to be above 80%, so that the returned gas phase and liquid phase have suitable volume flow rates and ethylene / propylene molar contents, thereby preparing a polymer having more excellent mechanical properties.

[0127] The present application also discloses a system for preparing the olefin polymer of the first aspect of the present application or used in the method of the second aspect of the present application, wherein the system comprises a polymerization reactor, a compressor, a heat exchanger, and a separation device.

[0128] The top of the polymerization reactor is sequentially communicated with the compressor, the heat exchanger, and the separation device, for sequentially compressing, cooling, and gas-liquid separating the gas discharged from the top of the polymerization reactor, the top of the separation device obtaining a gas phase, and the bottom of the separation device obtaining a liquid phase;

[0129] The middle of the polymerization reactor is communicated with the bottom of the separation device, for introducing the liquid phase discharged from the bottom of the separation device into the polymerization reactor;

[0130] The bottom of the polymerization reactor is communicated with the top of the separation device, for introducing the gas phase from the top of the separation device into the polymerization reactor.

[0131] In the present application, the number of the separation devices can be selected in a wide range, and a person skilled in the art can select according to actual needs. Preferably, the number of the separation devices is 1-4.

[0132] In the present application, the number of the liquid phase feed ports in the polymerization reactor can be selected in a wide range, as long as the liquid phase discharged from the bottom of the separation device can be introduced into the polymerization reactor, and a person skilled in the art can select according to actual needs. Preferably, the number of the liquid phase feed ports in the polymerization reactor is 2-12.

[0133] In the present application, the type of the polymerization reactor can be selected in a wide range, and a person skilled in the art can select according to actual needs. Preferably, the polymerization reactor is a fluidized bed reactor.

[0134] According to a particularly preferred embodiment of the present application, the superficial gas velocity of the fluidized bed polymerization reactor is 0.2-1 m / s.

[0135] According to a particularly preferred embodiment of the present application, the liquid phase feed ports are uniformly and symmetrically distributed on the side wall of the polymerization reactor. In the present application, the symmetric distribution refers to axial symmetry, and the height difference between adjacent liquid phase feed ports is 100-1500 mm.

[0136] In the present application, the polymerization reactor can be divided into four different polymerization zones according to the concentration of each reactant in the olefin monomer, as shown in Figure 1. Among them, there is a polypropylene zone in the central zone of the polymerization reactor, in which propylene polymerization is the main reaction; there is a rubber zone outside the polypropylene zone, in which ethylene-propylene rubber is generated by polymerization; there is a block zone outside the rubber zone, in which ethylene-propylene block is generated by polymerization; and there is a polyethylene zone at the bottom of the polymerization reactor, in which ethylene polymerization is the main reaction. The size of the above four zones is mainly affected by the ratio of the volume flow rate of the light component stream to the heavy component stream and the mole fraction of ethylene or propylene in the light component stream and the heavy component stream. By changing the above parameters, the content of each structure in the polymer can be changed, thereby changing the mechanical properties of the polymer.

[0137] The third aspect of the present application provides an olefin polymer prepared by the above method.

[0138] The method and system of the present application will be further described in combination with Figure 1.

[0139] (1) The catalyst, polymer, and olefin monomer are introduced into the polymerization reactor 1 to perform polymerization reaction in the presence of the catalyst, thereby obtaining an olefin polymer;

[0140] (2) The gas that does not participate in the reaction and is not completely reacted is discharged from the top of the polymerization reactor 1, thereby obtaining a circulating gas;

[0141] (3) The circulating gas is introduced into the compressor 2 from the inlet of the compressor 2 to be compressed, and is discharged from the outlet of the compressor 2 to be introduced into the inlet of the heat exchanger 3 to be cooled, thereby obtaining a gas-liquid mixture;

[0142] (4) The gas-liquid mixture is introduced into the side wall of the fractionating column 4, and then is separated, thereby obtaining a heavy component stream and a light component stream;

[0143] (5) The light component stream is discharged from the top of the fractionating column 4 and introduced into the bottom of the polymerization reactor 1; at the same time, the heavy component stream is discharged from the bottom of the fractionating column 4 and introduced into the side wall of the polymerization reactor 1.

[0144] The composition test method of the polymers prepared in the following examples and comparative examples is the same as the test method described in the specific embodiment.

[0145] The present application will be described in detail through examples below. In the following examples, if not specifically stated, the chemical reagents used in the present application are commercially available products without further treatment. Among them, the weight average molecular weight of the propylene polymer is 200000 g / mol.

[0146] In the following examples, a universal testing machine (CMT 4204) is used to test the flexural modulus of the polymer. The standard sample size is 4.0 mm in thickness, 10.0 mm in width, and 80.0 mm in length. The standard sample is also placed in a constant temperature oven at 23°C for more than 48 hours. The flexural rate is 2 mm / min. Each group of samples is tested 3-5 times to obtain the flexural modulus of the material.

[0147] The impact strength test uses a cantilever beam impact, the size of the pendulum is 5.5J, and the test method is in accordance with GBT1843-2008. The impact test sample size is 4mm (thickness) x 10mm (width) x 80mm (length). A 45° V-shaped notch with a depth of 2mm needs to be prepared in the middle of the sample before testing, and all samples need to be placed in a constant temperature environment at 23°C for not less than 48 hours to eliminate stress. In order to obtain reliable data, each group of samples is tested in parallel for 3-5 times, and the average value is taken as the impact strength index of the material. When the impact test at low temperature is carried out, the sample needs to be placed in the matched incubator set at the corresponding temperature for two hours, and the incubator is cooled by liquid nitrogen. Each group of samples is tested in parallel for 3-5 times, and the average value is taken as the impact strength index of the material.

[0148] Example 1

[0149] (1) Add ethylene, propylene, 0.059 kg of nitrogen, 3 g of Ziegler-Natta catalyst, hydrogen and 10 kg of propylene polymer into a 50 L fluidized bed reactor for reaction. The temperature in the fluidized bed reactor is controlled at 70°C, and the pressure in the fluidized bed reactor is controlled at about 2 MPa by adjusting the amount of fresh feed of ethylene and propylene. The molar ratio of hydrogen to propylene in the reactor is 0.08 mol / mol, and the propylene concentration is 75 mol%.

[0150] (2) After the mixed gas is reacted in the fluidized bed reactor for 30 min, the mixed gas that has not participated in the reaction and has not been completely reacted is discharged from the top of the column to obtain a circulating gas.

[0151] (3) The circulating gas is first compressed to 2.5 MPa (0.5 MPa pressure increase), and then the temperature is reduced to 35°C to obtain a gas-liquid mixture.

[0152] (4) The gas-liquid mixture is introduced into a fractionating column for separation. The gas phase accounts for 0.8 in the gas-liquid mixture introduced into the fractionating column, and the volume flow rate is 84.06 m 3 / h; the gas phase obtained after separation is discharged from the top of the fractionating column, and the volume flow rate of the gas phase is 64.21 m 3 / h, and the molar fraction of ethylene in the gas phase is 82.34%; the liquid phase obtained after separation is discharged from the bottom of the fractionating column, and the volume flow rate of the liquid phase is 2.76 m 3h, the mole fraction of propylene in the liquid phase is 86.75%.

[0153] (5) The gas phase is returned to the bottom of the fluidized bed reactor, and the liquid phase is returned to the side wall of the fluidized bed reactor through a nozzle. The volume flow rate of the gas phase and the liquid phase when returned is the same as the speed at which they are discharged from the fractionating column.

[0154] (6) After the gas phase and the liquid phase begin to return to the fluidized bed reactor, the solid product is discharged from the bottom of the fluidized bed reactor to obtain polymer 1.

[0155] Examples 2-5

[0156] The preparation steps are the same as in Example 1, except that in step (4), the relevant parameters of the gas-liquid mixture, the gas phase, and the liquid phase are shown in Table 2. The obtained products are polymers 2-5, respectively.

[0157] Comparative Examples 1 and 2

[0158] The preparation steps are the same as in Example 1, except that in step (4), the relevant parameters of the gas-liquid mixture, the gas phase, and the liquid phase are shown in Table 1. The obtained products are polymers D1 and D2.

[0159] Table 1

[0160] The weight average molecular weight, the number average molecular weight, the content of each component, the crystallinity of different components, the vinyl content, the flexural modulus, and the Izod impact strength of the olefin polymer were tested, and the results are shown in Table 2 or Table 3.

[0161] Table 2

[0162] Table 1 continued

[0163] " / " indicates that the first interface and the second interface are not present in the olefin polymer.

[0164] Table 2

[0165] As can be seen from Table 2 and Table 3, when the olefin polymer includes four components with specific compositions and contents, the olefin polymer has a flexural modulus and an Izod impact strength.

[0166] Further, as can be seen from Table 1, controlling the separation factor to be above 80% and ensuring that the volume flow rate of the gas phase (the light component stream) is 5-80 times the volume flow rate of the liquid phase (the heavy component stream) can prepare four components with specific compositions and contents, and the final olefin polymer obtains more excellent flexural modulus and Izod impact strength.

[0167] Figure 2 is the phase morphology and copolymer composition distribution results of polymer D1 and polymer 5 characterized by atomic force microscopy-infrared technique (AFM-IR). Among them, Figure 2a), Figure 2c), Figure 2e) are the height map (labeled points 1-8) representing the phase distribution of polymer D1, the IR spectrum obtained at the red rectangular position (the range including labeled points 1-8), and the normalized result of ethylene unit content (ethylene unit at labeled points 1-8), respectively; Figure 2b), Figure 2d), Figure 2f) are the height map (labeled points 1-8) representing the phase distribution of polymer 5, the IR spectrum obtained at the red rectangular position (the range including labeled points 1-8), and the normalized result of ethylene unit content (ethylene unit at labeled points 1-8), respectively. The core-shell structure dispersed phase of both polymer D1 and polymer 5 can be clearly observed in the AFM height map and IR spectrum, which is uniformly distributed in the polypropylene matrix in the form of island, the particle size distribution range is narrow, and the obvious core-shell structure characteristics are presented. It is worth noting that the core-shell particle structure and composition of the two are significantly different.

[0168] The AFM-IR spectrum is normalized to 1378 cm -1 characteristic peak of PP methyl symmetric deformation band, which is derived from polypropylene and polyethylene, and the relative intensity of 1456 cm -1 methylene band symmetric C-H bending at this position can well indicate the relative ethylene structural unit content. As shown in Figure 2a), Figure 2c), Figure 2e), the intensity at labeled points 1, 2 and 3 is lower at the 1456 cm -1 characteristic peak, indicating that it belongs to the polypropylene segment (i.e. component (i)). Labeled points 4 and 5 are located at the interface (i.e. the first interface) between the polypropylene matrix and the dispersed phase (including the core mainly composed of component (ii) and the shell layer mainly composed of component (iv)), and the ethylene content is basically the same as that of labeled points 6, 7 and 8 in the dispersed phase. The ethylene content distribution inside the dispersed phase is very uniform, and no significant composition mutation is found at the interface between the two phases, so the microphase interface compatibility in polymer D1 is limited.

[0169] As shown in Figure 2b), Figure 2d), Figure 2f), labeled points 1 and 2 have lower intensity at 1456 cm -1The intensity at the characteristic peak is very low, indicating that it is located in the polypropylene segment (i.e. component (i)), which is consistent with the result from the AFM height map. Marked point 3 is located near the interface between the polypropylene segment (i.e. component (i)) and the core-shell dispersed phase (i.e. the first interface), with a higher ethylene content, indicating that the long propylene segment of the block copolymer (i.e. component (iii)) forms a co-crystallization with the propylene segment of the polypropylene matrix, and the ethylene segment, which is incompatible with the propylene segment, is expelled to the interface between the polypropylene matrix and the dispersed phase (i.e. the first interface). Marked points 7 and 8 have the highest ethylene content, indicating that the core of the core-shell dispersed particle is rich in polyethylene (i.e. component (ii)), the polyethylene segment). Notably, marked point 5 is located near the interface between the polyethylene core and the rubber phase (i.e. component (iv)) shell, where the ethylene content is the lowest, which is obviously different from the long ethylene segment and the random rubber phase, which indicates that component (iii) with specific aggregation behavior is distributed at this position, and the long ethylene segment of the block copolymer of component (iii) co-crystallizes with the polyethylene (i.e. component (i)), and the incompatible polypropylene segment is induced to aggregate at the interface between the polyethylene core and the rubber phase.

[0170] It can also be seen from Figure 2 that controlling the separation factor to be above 80% and ensuring that the volume flow rate of the gas phase (light component stream) is 5-80 times the volume flow rate of the liquid phase (heavy component stream) can promote the migration of the block copolymer in the rubber phase (component iv) to the interface, and the long propylene segment thereof can co-crystallize with the polypropylene matrix (component i), greatly improving the interfacial bonding ability of the polypropylene matrix and the rubber phase, and the ethylene segment in the rubber phase (component iv) can co-crystallize with the polyethylene core of the core-shell particle (the core mainly composed of component ii, and the shell layer mainly composed of component iv), making the interface between the polyethylene core and the rubber phase (component iii) stronger, achieving the effect of enhanced multi-phase interface interaction and improved compatibility.

Claims

1. An olefin polymer, characterized by, The olefin polymer comprises four components: Component (i): a fraction of the olefin polymer obtained by temperature rising elution fractionation at an elution temperature greater than 140℃; Component (ii): a fraction of the olefin polymer obtained by temperature rising elution fractionation at an elution temperature greater than 100℃ and not higher than 140℃; Component (iii): a fraction of the olefin polymer obtained by temperature rising elution fractionation at an elution temperature greater than 50℃ and not higher than 100℃; Component (iv): a fraction of the olefin polymer obtained by temperature rising elution fractionation at an elution temperature greater than 0℃ and not higher than 50℃; The content of component (i) is 20-80wt%, the content of component (ii) is 2-30wt%, the content of component (iii) is 5-30wt%, and the content of component (iv) is 10-50wt%.

2. The olefin polymer of claim 1, wherein, The component (iii) and the component (iv) each independently comprises at least two of ethylene segment, propylene segment and α-olefin segment.

3. The olefin polymer of claim 1 or 2, wherein, The content of ethylene group in component (iii) is 20-30wt%; And / or, the content of ethylene group in component (iv) is 30-50wt%.

4. The olefin polymer of any one of claims 1-3, wherein, The weight average molecular weight of the olefin polymer is 5 x 10 4 g / mol - 55 x 10 4 g / mol, the number average molecular weight is 3 x 10 4 g / mol - 15 x 10 4 g / mol; and the molecular weight distribution is 3 - 8.

5. The olefin polymer of any one of claims 1-4, wherein, The component (iii) has a crystallinity of 20-30%; And / or, the component (iv) has a crystallinity of less than 1%. The olefin polymer comprises a continuous phase, and a dispersed phase dispersed in the continuous phase, and a first interface formed by the dispersed phase and the continuous phase; 6. The olefin polymer of any one of claims 1-5, wherein, The continuous phase comprises component (i); The dispersed phase comprises a core mainly composed of component (ii), and a shell layer mainly composed of component (iv); The first interface comprises component (iii). The crystallinity of the first interface is 20-65%; 7. The olefin polymer of claim 6, wherein, And / or, the crystallinity of a second interface formed by the core and the shell layer in the dispersed phase is 5-50%. The method comprises the following steps:

8. A process for the preparation of an olefin polymer, characterized in that, (1) polymerizing a polymer and an olefin monomer in the presence of a catalyst to obtain an olefin polymer; (2) discharging the gas not involved in the reaction and not completely reacted in step (1) to obtain a circulating gas; (3) compressing and / or cooling the circulating gas to obtain a gas-liquid mixture; (4) separating the gas-liquid mixture to obtain a heavy component stream and a light component stream; (5) returning the heavy component stream and the light component stream to step (1) respectively; The olefin monomer comprises propylene, ethylene and optional α-olefin; The separation factor of the heavy component stream and the light component stream is more than 80%; the volume flow rate of the light component stream returned to step (1) is 5-80 times the volume flow rate of the heavy component stream returned to step (1). In step (1), the polymer is a propylene polymer; 9. The method of claim 8, wherein, Preferably, in step (4), the separation factor of the heavy component stream and the light component stream is 80-98%; Preferably, in step (5), the volume flow rate of the light component stream returned to step (1) is 10-70 times the volume flow rate of the heavy component stream returned to step (1); Preferably, in step (5), the heavy component stream comprises propylene, ethylene and optional α-olefin; ​ Preferably, in step (5), the molar fraction of propylene in the heavy component stream is 60-99% based on the total moles of propylene, ethylene and optional alpha-olefins; Preferably, in step (5), the light component stream comprises ethylene and propylene; Preferably, in step (5), the molar fraction of ethylene in the light component stream is 60-99% based on the total moles of propylene and ethylene.

10. The method of claim 8 or 9, wherein, The alpha-olefin has a carbon number of 18 or less, preferably butene and / or 1-hexene; Preferably, in step (1), the volume flow rates of the olefin monomers, the heavy component stream and the light component stream are such that the molar fraction of ethylene is 15-40%, the molar fraction of propylene is 55-80% and the molar fraction of alpha-olefins is 0-5% based on the total moles of ethylene, propylene and alpha-olefins.

11. The method of any of claims 8-10, wherein, In step (1), the polymerization reaction is carried out in the presence of a regulator; Preferably, the regulator comprises hydrogen; Preferably, the molar ratio of the regulator to propylene is 0.01-0.5:1; Preferably, in step (1), the polymerization reaction is carried out in the presence of a protective gas.

12. The method of any of claims 8-11, wherein, The pressure of the polymerization reaction is 0.5-5 MPa and the temperature of the polymerization reaction is 50-100°C; Preferably, in step (1), the catalyst is selected from the group consisting of a Ziegler-Natta type catalyst and / or a metallocene catalyst, more preferably a Ziegler-Natta type catalyst; Preferably, in step (1), the polymerization reaction is carried out in a fluidized bed reactor.

13. The method of any of claims 8-12, wherein, In step (3), the circulating gas is compressed to a pressure of 0.01-1 MPa; Preferably, in step (3), the circulating gas is cooled to a temperature of 5°C-60°C; Preferably, in step (4), the temperature of separation is 20-60°C and the separation pressure is 1-3 MPa.

14. An olefin polymer produced by the method of any one of claims 8-13.

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