Polyolefin polymers and systems and methods for polyolefin polymerization

Abstract

The present invention relates to a polyolefin polymer, and a polymerization system and a polymerization method for preparing the same, the polyolefin polymer comprising: a core; and a shell wherein the core has a density of from 0.857 g / cm3 to 0.910 g / cm3, the shell has a density of from 0.890 g / cm3 to 0.940 g / cm3, and the density of the shell is higher than the density of the core.

Description

TECHNICAL FIELD

[0001] Cross Reference to Related Applications

[0002] This application claims priority to and the benefit of Korean Patent Application Nos. 10-2023-0122347 and 10-2024-0003448, filed on September 14, 2023, and January 9, 2024, respectively, with the Korean Intellectual Property Office, the entire disclosures of which are incorporated herein by reference. TECHNICAL FIELD

[0004] The present disclosure relates to polyolefin polymers and systems and methods for polyolefin polymerization. BACKGROUND

[0005] Linear low density polyethylene (LLDPE) is widely produced by a gas phase process using a fluidized bed reactor. Specifically, LLDPE is produced by copolymerizing ethylene monomers and comonomers in the presence of a catalyst.

[0006] In producing polymers such as linear low density polyethylene, large comonomers having four or more carbon atoms compared to ethylene monomers are used. Since the comonomers have a low vapor pressure, they condense in the polymerization reactor and are absorbed by the polymer, causing the polymer to swell. Polymers containing a large amount of comonomers have a low degree of crystallinity and a melting point, resulting in a sticky wet resin inside the polymerization reactor. These sticky polymers hinder fluidization in the reactor due to their stickiness, adversely affecting the continuous operation of the gas phase polymerization reactor.

[0007] U.S. Patent Publication No. 4,994,534 discloses a method of producing a sticky polymer such as ethylene / propylene rubber by adding silica or clay during polymerization. The addition of these materials to the reactor not only makes the polymer unusable for a variety of applications, but also causes contamination of heat exchangers, compressors, and other reactor systems.

[0008] Similarly, U.S. Patent Publication No. 4,970,279 and International Patent Publication No. WO 88 / 02379 disclose a method of adding powdered inorganic materials such as silica or alumina to a reactor. U.S. Patent Publication Nos. 5,100,979 and 5,106,926 disclose a method of preparing ethylene / 1-octene copolymers using a specific titanium-based catalyst system or a specific vanadium-based catalyst system that is not commercially available. Further, U.S. Patent Publication No. 5,017,665 discloses a method of producing a polymer having an extremely low molecular weight and a low density by preparing ethylene / 1-butene / 1,4-hexadiene in the presence of a metallocene / aluminoxane catalyst system. U.S. Patent Publication No. 5,712,353 discloses a method of preparing a relatively high molecular weight and low density elastomer using a metallocene catalyst. The method enables the preparation of a high molecular weight, low density elastomer at a temperature of 50°C or higher. However, the low melting point and tackiness of the elastomer can disadvantageously cause a high likelihood of process problems that hinder continuous operation at high temperatures.

[0009] Further, the conventional method uses a jacket installed outside the reactor to remove internal heat, and removes heat by heat exchange with cooling water supplied to the jacket. However, sufficient heat removal requires a large heat exchange area, which inevitably makes the external jacket excessively long.

[0010] [Related Art Documents]

[0011] [Patent Documents]

[0012] (Patent Document 1) 1. U.S. Patent Publication No. 4,994,534

[0013] (Patent Document 2) 2. U.S. Patent Publication No. 4,970,279

[0014] (Patent Document 3) 3. International Patent Publication No. WO 88 / 02379

[0015] (Patent Document 4) 4. U.S. Patent Publication No. 5,100,979

[0016] (Patent Document 5) 5. U.S. Patent Publication No. 5,106,926

[0017] (Patent Document 6) 6. U.S. Patent Publication No. 5,017,665

[0018] (Patent Document 7) 7. U.S. Patent Publication No. 5,712,353 SUMMARY

[0019] TECHNICAL PROBLEM

[0020] The present invention provides a low-density polyolefin polymer including a core and a shell, wherein the density of the shell is higher than the density of the core. In addition, the present invention provides a system and a method for polymerization of a low-density polyolefin polymer, thereby preventing process stability deterioration due to poor continuous operation by tackiness when the surface of the polymer has a low density.

[0021] Another aspect of the present disclosure is to provide a slurry polymerization reactor including a heat exchanger, thereby overcoming the drawbacks associated with the use of an external jacket in which the jacket has an excessively long length.

[0022] Technical Solution

[0023] According to the present disclosure, the above and other objects can be achieved by providing a polyolefin polymerization system including one or more slurry polymerization reactors configured to slurry polymerize a supplied feed stream in the presence of a catalyst to produce a slurry reaction product including a prepolymer, wherein the feed stream includes monomers and comonomers, and each slurry polymerization reactor includes a loop including one or more reactors, one or more polymer outlets, one or more monomer inlets, one or more heat exchangers, and one or more circulation pumps.

[0024] The shell can be formed by the slurry polymerization reactor.

[0025] The heat exchanger can be shell-and-tube type.

[0026] The heat exchanger can have a cooling water flow rate of 1 m / sec or more, preferably 3 m / sec or more, and a heat transfer efficiency of 0.3 Mcal / m 2 × hr × K or more, preferably 0.6 Mcal / m 2 × hr × K or more.

[0027] The polyolefin polymerization system can further include one or more gas phase polymerization reactors configured to receive the slurry reaction product or the slurry reaction product and the feed stream, and gas phase polymerize the slurry reaction product or the slurry reaction product and the feed stream to produce a gas phase reaction product including a final polymer.

[0028] The core can be formed by the gas phase polymerization reactor.

[0029] The final polymer can include the core and a shell having a density higher than the core to provide two or more density distributions, and the slurry polymerization reactor can have an operating temperature of 20℃ to 70℃ and can be higher than the operating temperature of the gas phase polymerization reactor.

[0030] The core can have a density of 0.857 g / cm 3 to 0.910 g / cm 3and the density of the shell can be 0.890 g / cm 3 to 0.940 g / cm 3 and the density of the shell can be higher than the density of the core.

[0031] The final polymer can have at least one of the following properties (a) to (h):

[0032] (a) a melt index of 0.1 g / 10 minutes to 5.0 g / 10 minutes (MIE, 2.16 kg load, 190 °C);

[0033] (b) a density of 0.870 g / cm 3 to 0.900 g / cm 3 ;

[0034] (c) two or more melting temperatures (T m );

[0035] (d) a first melting temperature (T m1 ) and a second melting temperature (T m2 ), wherein the difference between T m1 and T m2 is 30 °C to 70 °C;

[0036] (e) a first melting temperature (T m1 ) of 45 °C to 85 °C, and a second melting temperature (T m2 ) of 80 °C to 125 °C;

[0037] (f) two or more crystallization temperatures (T c );

[0038] (g) a first crystallization temperature (T c1 ) of 40 °C to 100 °C, and a second crystallization temperature (T c2 ) of 70 °C to 110 °C; and

[0039] (h) two or more peaks in a temperature rising elution fractionation (TREF) chromatogram at a temperature of 35 °C or higher, wherein the area of the graph at a temperature of 60 °C or higher is 5% or greater of the total chromatogram area.

[0040] The polyolefin polymerization system can include a first slurry polymerization reactor configured to slurry polymerize a supplied feed stream in the presence of a catalyst to produce a slurry reaction product comprising a pre-polymer, and a first gas phase polymerization reactor configured to receive the slurry reaction product or the slurry reaction product and the feed stream and gas phase polymerize the slurry reaction product or the slurry reaction product and the feed stream to produce a gas phase reaction product comprising a final polymer.

[0041] The polyolefin polymerization system can include a first slurry polymerization reactor configured to slurry polymerize a supplied feed stream in the presence of a catalyst to produce a first slurry reaction product comprising a pre-polymer, a second slurry polymerization reactor configured to receive the first slurry reaction product from the first slurry polymerization reactor or the first slurry reaction product from the first slurry polymerization reactor and the feed stream and slurry polymerize the first slurry reaction product or the first slurry reaction product and the feed stream to produce a second slurry reaction product comprising a pre-polymer, a first gas phase polymerization reactor configured to receive the second slurry reaction product from the second slurry polymerization reactor or the second slurry reaction product from the second slurry polymerization reactor and the feed stream and gas phase polymerize the second slurry reaction product or the second slurry reaction product and the feed stream to produce a first gas phase reaction product comprising a final polymer, and a second gas phase polymerization reactor configured to receive the first gas phase reaction product from the first gas phase polymerization reactor or the first gas phase reaction product from the first gas phase polymerization reactor and the feed stream and gas phase polymerize the first gas phase reaction product or the first gas phase reaction product and the feed stream to produce a second gas phase reaction product comprising a final polymer.

[0042] The catalyst can be a metallocene single site catalyst.

[0043] The monomer can be ethylene.

[0044] The comonomer can include one or more selected from the group consisting of 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, and 1-octene.

[0045] The slurry polymerization reactor can operate at a temperature of 40°C to 60°C, and the gas phase polymerization reactor can operate at a temperature of 30°C to 50°C.

[0046] The gas phase polymerization reactor can operate at a temperature less than the MIT 15 (15 wt% melt onset temperature) as measured according to ASTM 3417-83.

[0047] The second gas phase polymerization reactor can be operated in a high adsorption mode in which an adsorbent is used in an amount of 0.1 to 30 parts by weight based on 100 parts by weight of the circulating gas stream.

[0048] Advantageous Effects

[0049] The present disclosure can achieve efficient removal of heat inside the reactor by using one or more slurry polymerization reactors and one or more gas phase polymerization reactors and introducing a heat exchanger into the slurry polymerization reactor and thus has the effect of improving the productivity of the polymer. In addition, by controlling the operating conditions of each of the slurry polymerization reactor and the gas phase polymerization reactor, process stability can be ensured when preparing a polyolefin polymer. The polyolefin polymer thus prepared can include a core and a shell, and can have a density distribution structure in which the density of the shell is higher than the density of the core. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 The structure of a slurry polymerization reactor according to one embodiment of the present disclosure is illustrated.

[0051] Figure 2a The structure of a first slurry polymerization reactor and a first gas phase polymerization reactor according to one embodiment of the present disclosure is illustrated.

[0052] Figure 2b The structure of a first slurry polymerization reactor, a second slurry polymerization reactor, and a first gas phase polymerization reactor according to one embodiment of the present disclosure is illustrated.

[0053] Figure 2c The structure of a first slurry polymerization reactor, a first gas phase polymerization reactor, and a second gas phase polymerization reactor according to one embodiment of the present disclosure is illustrated.

[0054] Figure 2d The structure of a first slurry polymerization reactor, a second slurry polymerization reactor, a first gas phase polymerization reactor, and a second gas phase polymerization reactor according to one embodiment of the present disclosure is illustrated.

[0055] Figure 3 The structure of a shell-and-tube heat exchanger according to one embodiment of the present disclosure is illustrated.

[0056] Figure 4a A cross-sectional SEM image of a prepolymer prepared in Example 2.

[0057] Figure 4b A cross-sectional SEM image of a final polymer prepared in Example 2.

[0058] Figure 4cSEM images before and after the final polymer prepared in Example 2 is dissolved in xylene are shown.

[0059] Figure 5 Thermal rising elution fractionation (TREF) chromatograms obtained by measuring TREF values of the final polymers prepared in Example 5 and Comparative Example 3 as a function of temperature. DETAILED DESCRIPTION

[0060] The terms and words used in the present description and claims should not be interpreted as being limited to the ordinary or dictionary meanings, but should be interpreted to appropriately describe the technology of the present disclosure in the best way based on the principles of the inventor's intention, in accordance with the technical spirit and scope of the present disclosure.

[0061] As used herein, the term "stream" can refer to the flow of fluid within a process, and can also refer to the fluid itself as it flows through a conduit. In particular, the term "stream" can refer to both the fluid flowing through a conduit connecting units, and the flow of such fluid. The fluid can be a gas or a liquid, and does not exclude the presence of solid components in the fluid.

[0062] Hereinafter, embodiments of the present disclosure will be described in detail so that those skilled in the art can easily practice the present disclosure. However, the embodiments can be implemented in various different forms, and should not be construed as being limited to the embodiments described herein.

[0063] In one embodiment, the polyolefin polymer includes a core and a shell, wherein the density of the core is 0.857 g / cm 3 to 0.910 g / cm 3 , the density of the shell is 0.890 g / cm 3 to 0.940 g / cm 3 , and the density of the shell is higher than the density of the core.

[0064] As described above, the polyolefin polymer has a core-shell structure including a core and a shell surrounding the core, each having the above-described density range. Since the shell (i.e., the surface of the polymer) has a relatively high density, stickiness that can be generated when the surface density in the polymerization step is low during the preparation of a low-density polymer can be reduced. Accordingly, fluidization within a gas phase polymerization reactor is not hindered, aggregation between polymer particles is prevented, and plugging of peripheral equipment such as conduits and heat exchangers is minimized, thereby enabling stable continuous operation.

[0065] In one embodiment, the polyolefin polymer can exhibit one or more of the following properties (a) to (h). For example, the polymer can exhibit two or more or all of the following properties (a) to (h).

[0066] (a) a melt index (MIE, 2.16 kg load, 190°C) of 0.1 g / 10 minutes to 5.0 g / 10 minutes;

[0067] (b) a density of 0.870 g / cm 3 to 0.900 g / cm 3 ;

[0068] (c) two or more melting temperatures (T m );

[0069] (d) a first melting temperature (T m1 ) and a second melting temperature (T m2 ), wherein the difference between T m1 and T m2 is 30°C to 70°C;

[0070] (e) a first melting temperature (T m1 ) of 45°C to 85°C, and a second melting temperature (T m2 ) of 80°C to 125°C;

[0071] (f) two or more crystallization temperatures (T c );

[0072] (g) a first crystallization temperature (T c1 ) of 40°C to 100°C, and a second crystallization temperature (T c2 ) of 70°C to 110°C; and

[0073] (h) two or more peaks in a temperature rising elution fractionation (TREF) chromatogram at temperatures of 35°C or greater, wherein the percentage of the area of the graph at 60°C or greater to the total area of the graph is 5% or greater.

[0074] In (a), the melt index (MIE, 2.16 kg load, 190°C) refers to the melt index measured according to ASTM D1238 at 190°C under a load of 2.16 kg. The melt index of the polyolefin polymer can be, for example, 0.1 g / 10 minutes to 5.0 g / 10 minutes, 0.5 g / 10 minutes to 4.0 g / 10 minutes, or 0.6 g / 10 minutes to 3.2 g / 10 minutes. Because the polymer has a melt index within these ranges, the polymer can exhibit improved process stability and processability.

[0075] In (b), the density refers to the density measured according to ASTM D1505 using a density gradient column method. The density can be, for example, 0.870 g / cm 3 to 0.900 g / cm 3, preferably 0.885 g / cm 3 to 0.890 g / cm 3 , thereby providing a low density polyolefin polymer.

[0076] In (c), the melting temperature (T m ) refers to the melting temperature measured according to ASTM 3417-83. The polyolefin polymer can exhibit two or more melting temperature distributions, such as two to four, two to three, or two melting temperature distributions.

[0077] In (d), the first melting temperature (T m1 ) can be 30 °C to 70 °C, 31 °C to 68 °C, or 33 °C to 38 °C different from the second melting temperature (T m2 ).

[0078] In (e), the first melting temperature can be 45 °C to 85 °C, 50 °C to 85 °C, or 60 °C to 70 °C, and the second melting temperature can be 80 °C to 125 °C, 90 °C to 120 °C, or 95 °C to 110 °C.

[0079] In (f), similar to the melting temperature, the crystallization temperature (T c ) can refer to the crystallization temperature of the polyolefin polymer measured according to ASTM 3417-83. The polyolefin polymer can have two or more crystallization temperature distributions. For example, the polyolefin polymer can have two to four, two to three, or two crystallization temperature distributions.

[0080] In (g), the polyolefin polymer can have a first crystallization temperature (T c1 ) and a second crystallization temperature (T c2 ). The first crystallization temperature can range from 40 °C to 100 °C, 43 °C to 97 °C, or 44 °C to 50 °C. Further, the second crystallization temperature can range from 70 °C to 110 °C, 72 °C to 109 °C, or 74 °C to 87 °C.

[0081] In (h), a temperature rising elution fractionation (TREF) chromatogram can be obtained by analyzing the polyolefin polymer using a cross-fractionation chromatography (CFC, PolymerChar CFC-2) instrument. The temperature rising elution fractionation (TREF) chromatogram of the polyolefin polymer can exhibit two or more, two to five, or two peaks at temperatures of 35 °C or greater. The percentage of the area of the graph at 60 °C or greater to the total area of the graph can be 5% or greater, 5% to 55%, or 5% to 50% in the temperature rising elution fractionation (TREF) chromatogram. As described above, the presence of two or more peaks in the temperature rising elution fractionation (TREF) chromatogram indicates that the polyolefin polymer has a density gradient. Further, the percentage of the area of the graph at 60 °C or greater to the total area of the graph is 5% or greater, indicating that a relatively high density shell formed by slurry polymerization that elutes at high temperature forms well.

[0082] In one embodiment, the shell can be formed by a slurry polymerization reaction in the polyolefin polymerization system or process described below. Specifically, in the polyolefin polymer, a hollow, relatively dense shell can be formed first.

[0083] The density of the shell can be, for example, 0.890 g / cm 3 to 0.940 g / cm 3 , 0.895 g / cm 3 to 0.930 g / cm 3 , or 0.900 g / cm 3 to 0.922 g / cm 3 .

[0084] The melt flow index (MIE (2.16 kg load, 190 °C)) of the shell can be, for example, 0.01 g / 10 minutes to 5.0 g / 10 minutes, 0.05 g / 10 minutes to 3.5 g / 10 minutes, or 0.05 g / 10 minutes to 2.0 g / 10 minutes.

[0085] The melting temperature of the shell can be, for example, 80 °C to 125 °C, 90 °C to 120 °C, or 95 °C to 110 °C.

[0086] The shell can have a single peak in a temperature rising elution fractionation (TREF) chromatogram at temperatures of 60 °C or greater.

[0087] In one embodiment, the core can be formed by a gas phase polymerization reaction in the polyolefin polymerization system or process described below. Specifically, in the polyolefin polymer, the core can be formed by filling the hollow portion of the shell formed by a slurry polymerization reaction with a relatively low density product.

[0088] The density of the core can be, for example, 0.857 g / cm 3to 0.910 g / cm 3 , 0.857 g / cm 3 to 0.900 g / cm 3 , or 0.857 g / cm 3 to 0.898 g / cm 3 .

[0089] The core can have a melting temperature of, for example, 45°C to 85°C, 50°C to 85°C, or 60°C to 70°C.

[0090] The core and the shell can have a weight ratio of 40:60 to 90:10, 50:50 to 80:20, or 50:50 to 70:30. By forming the core and the shell within the above weight ratio, a low-density polyolefin polymer can be provided while also preventing the relatively low-density core from leaking to the surface of the polymer, thereby further improving process stability.

[0091] As described above, the polyolefin polymer having the core-shell structure in which the core and the shell have different physical properties not only exhibits a low-density property but also forms a surface (hollow shell) having a relatively high density while the relatively low-density core fills the inside of the shell. Based on this structure, tackiness and moisture-related adhesion that can occur when the surface density of the polymer is low are reduced, thereby preventing process stability from deteriorating.

[0092] The polyolefin polymer can have a melt index (MIE, 2.16 kg load, 190°C) of, for example, 0.1 g / 10 minutes to 5.0 g / 10 minutes, 0.5 g / 10 minutes to 4 g / 10 minutes, or 0.6 g / 10 minutes to 3.2 g / 10 minutes.

[0093] In one embodiment, a system for polymerization of a polyolefin polymer includes one or more slurry polymerization reactors configured to slurry polymerize a supplied feed stream in the presence of a catalyst to produce a slurry reaction product comprising a prepolymer, wherein the feed stream comprises monomers and comonomers, and the slurry polymerization reactor comprises: a loop comprising one or more reactors, one or more polymer outlets, one or more monomer inlets, one or more heat exchangers, and one or more circulation pumps.

[0094] The shell can be formed by the slurry polymerization reactor.

[0095] The heat exchanger cools the slurry and returns the cooled slurry to the reactor, thereby effectively removing polymerization heat from the reactor. One or more heat exchangers, for example, two or three heat exchangers, can be provided in each slurry polymerization reactor system.

[0096] The heat exchanger can be selected from a group consisting of a double pipe heat exchanger, a shell and tube heat exchanger, a plate heat exchanger, a spiral heat exchanger, and a spiral plate heat exchanger, and is preferably a shell and tube heat exchanger. The shell and tube heat exchanger provides a large heat transfer area despite its compact structure, and enables sufficient heat removal even in a limited installation space.

[0097] Specifically, Figure 3 One example of a shell and tube heat exchanger is shown. As shown, the shell and tube heat exchanger extends vertically and includes a head at an upper end and a lower end, a tube sheet, and a nozzle, and a tube bundle, a shell, and a baffle in a central portion thereof. Figure 3

[0098] The head defines an area through which a heat transfer medium enters or exits the heat exchanger. The tube sheet fixes a plurality of tube bundles and maintains a seal between the tube bundles and the shell, thereby ensuring structural stability of the heat exchanger. The nozzle provides a flow path for cooling water to enter or exit the heat exchanger and controls fluid flow.

[0099] The heat exchanger can include a plurality of tube bundles through which cooling water flows to effectively transfer heat from the reactor to the outside. The plurality of tube bundles can be arranged in parallel and closely packed to maximize the heat transfer area.

[0100] The shell is an external structure that surrounds the plurality of tube bundles, serves as a protective shell of the heat exchanger, and includes a space defined within the shell through which cooling water circulates, in which heat from the reactor is released to the outside through the space.

[0101] A plurality of baffles are installed within the shell, the baffles are spaced apart from each other and are alternately arranged in a zigzag structure. Such an arrangement intermittently changes the flow of cooling water, thereby increasing the contact time of the tube bundles with the cooling water and improving the heat exchange efficiency.

[0102] The heat exchanger can operate at a cooling water flow rate of 1 m / sec or more, preferably 3 m / sec or more, and can exhibit a heat transfer efficiency of 0.3 megacal / m 2 × hr × K or more, preferably 0.6 megacal / m 2 × hr × K or more. In this context, "hr" denotes hours and "K" denotes absolute temperature.

[0103] The slurry polymerization reactor of the present disclosure includes one or more circulation pumps configured to draw reactor contents and circulate the reactor contents through the heat exchanger. The circulation pump is preferably provided upstream of the heat exchanger, i.e., between the outlet of the polymerization reactor and the heat exchanger, but is not limited thereto.

[0104] ​The polyolefin polymerization system can also include one or more gas phase polymerization reactors configured to receive the slurry reaction product or the slurry reaction product and the feed stream and perform gas phase polymerization to produce a gas phase reaction product comprising the final polymer.

[0105] The core can be formed by the gas phase polymerization reactor.

[0106] The final polymer includes a core and a shell having a density higher than the density of the core, thereby exhibiting two or more density profiles. The slurry polymerization reactor can have an operating temperature of 20°C to 70°C and can be higher than the operating temperature of the gas phase polymerization reactor.

[0107] The polyolefin polymerization system can be a system for producing a final polymer (i.e., a polyolefin polymer).

[0108] In one embodiment, each of the one or more slurry polymerization reactors and each of the one or more gas phase polymerization reactors can be connected in series.

[0109] In one embodiment, a metallocene single-site catalyst can be used as the catalyst. The metallocene can be represented by the formula L n MQ p where M is a Group IIIB, Group IVB, Group VB, or Group VIB metal; Q is a hydrocarbyl group or a halogen having 1 to 20 carbon atoms; p is equal to the valence of M minus 2; and L is a ligand bonded to the metal M.

[0110] Such metallocene catalysts are known to exhibit higher activity and excellent copolymerizability compared to conventional Ziegler-Natta catalysts, thereby producing polyolefins having improved physical properties. The metallocene catalysts can be used as homogeneous catalysts and can be supported on a suitable support. For example, the support can include silicon oxide and / or aluminum oxide. In one particular example, the support can be silica having hydroxyl groups or other active hydrogen atom-containing functional groups and can have a porous spherical particle form.

[0111] The metallocene catalyst can be supported on the support with a cocatalyst, which can include an alkylaluminoxane. The alkylaluminoxane can include linear and / or cyclic alkylaluminoxane oligomers. When the alkylaluminoxane is a linear alkylaluminoxane oligomer, it can be represented by the formula R-(Al(R)-O) n -AlR2, and when the alkylaluminoxane is a cyclic alkylaluminoxane oligomer, it can be represented by the formula (-Al(R)-O- mwherein R is a C1-C8 alkyl group, preferably methyl; n is 1 to 40, preferably 10 to 20; and m is 3 to 40, preferably 3 to 20. Alkylaluminoxane is typically a mixture of oligomers having a broad molecular weight distribution and has an average molecular weight of 800 to 1,200.

[0112] In one embodiment, the feed stream can include monomers and comonomers.

[0113] The monomer can be ethylene.

[0114] The comonomer can include one or more selected from the group consisting of 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, and 1-octene. In a specific example, the comonomer can include one or more of 1-butene and 1-hexene.

[0115] The feed stream can also include a diluent. The diluent can include one or more of an inert gas and an alkane. The inert gas can include nitrogen, helium, neon, and the like, and the alkane can include butane, propane, isobutane, isopentane, hexane, isomers thereof, and the like. The process can include contacting the catalyst with the monomers and comonomers in the slurry polymerization reactor and the gas phase polymerization reactor using the diluent to produce the polyolefin polymer.

[0116] A system in which one or more slurry polymerization reactors and one or more gas phase polymerization reactors are sequentially arranged can be used to polymerize a feed stream including ethylene and comonomers in the presence of a catalyst to produce a polyolefin polymer. In a specific example, the polyolefin polymer can be a polyolefin elastomer, more specifically, a low density polyethylene.

[0117] In one embodiment, the slurry polymerization reactor can operate at a temperature of 20°C to 70°C, or 40°C to 60°C. The gas phase polymerization reactor can operate at a temperature lower than the slurry polymerization reactor, and can be, for example, 30°C to 50°C, or 35°C to 48°C. By operating each reactor at a reduced temperature to produce the final polymer as described above, viscosity and moisture related sticking of the resin that can impede fluidization within the reactor can be minimized, further improving process stability.

[0118] In one embodiment, the slurry polymerization reactor can be operated at a pressure of 5 K / G to 30 K / G, such as 10 K / G to 25 K / G, or 20 K / G to 25 K / G. The gas phase polymerization reactor can be adjusted to operate at a pressure equal to or lower than the slurry polymerization reactor. For example, depending on the operating temperature of the slurry reactor, the gas phase polymerization reactor can be operated at a pressure of 10 K / G to 20 K / G, or 10 K / G to 15 K / G. By operating each reactor at a reduced pressure, viscosity and moisture induced sticking that can interfere with the fluidization of the reactor can be minimized, thereby further improving process stability. As used herein, the pressure unit "K / G" refers to kg / cm 2 .

[0119] In one embodiment, a pre-polymer having a relatively high density and a hollow shell structure is prepared in a slurry polymerization by using a multi-stage polymerization of one or more slurry polymerization reactors and one or more gas phase polymerization reactors, followed by forming a polyolefin polymer (i.e., a polyolefin elastomer (POE)) within the hollow interior of the pre-polymer particles in a gas phase polymerization to produce a final polymer. The final polymer can exhibit the properties of a polyolefin elastomer.

[0120] In one embodiment, the molar ratio of ethylene to comonomer alpha-olefin in each reactor can be adjusted to 0.01 to 0.3 depending on the type of comonomer. For example, in the slurry polymerization reactor, the molar ratio of comonomer can be 0.01 to 0.3, 0.05 to 0.3, or 0.07 to 0.27 based on the total amount of monomers and comonomers. In the gas phase polymerization reactor, the molar ratio of comonomer can be 0.01 to 0.2, or 0.05 to 0.18 based on the total amount of monomers and comonomers. By employing different comonomer ratios in each reactor, a polymer having properties such as two or more melting temperatures or two or more crystallization temperatures can be produced. Such a polymer can have advantages in both processability and physical properties due to the high melting temperature and low glass transition temperature (T g ) of the polymer.

[0121] The pre-polymer produced in the slurry polymerization reactor can be present in an amount of 10 wt% to 60 wt% relative to the total amount of the final polymer. For example, the pre-polymer can be present in an amount of 20 wt% to 50 wt%, or 30 wt% to 50 wt% relative to the total final polymer. By controlling the weight ratio of the pre-polymer within this range, the overall density can be increased without compromising the physical properties of the final polymer, while firmly forming a shell of a relatively high density. Accordingly, the amount of polymer produced in the gas phase polymerization reactor that is exposed on the outer surface is minimized, thereby improving process stability.

[0122] In one embodiment, the gas phase polymerization reactor can be operated at a temperature lower than MIT 15 (15 wt% melting onset temperature) measured according to ASTM 3417-83. Specifically, a temperature lower than MIT 15 is selected to ensure process stability while maintaining a reduced reactor operating temperature. MIT 15 may be measured according to ASTM 3417-83 using a DSC instrument by performing a first scan from 25 °C to 200 °C at a heating rate of 10 °C / min and determining the temperature corresponding to 15 wt% melting area percentage.

[0123] For example, the temperature lower than MIT 15 in the gas phase polymerization reactor can be 40 °C to 80 °C, 40 °C to 70 °C, or 40 °C to 65 °C. When the gas phase polymerization reactor is operated at the same temperature as MIT 15 , polymer agglomeration can occur, such that process stability is reduced. At the same time, a reactor temperature that is too low to ensure process stability can cause a significant reduction in productivity. Furthermore, in the process of preparing a polyolefin polymer having a high comonomer content, as productivity is increased, a local area having a high comonomer concentration can be formed, which can increase the tackiness of the polymer and cause the formation of an undesirable polymer, thereby creating a process problem. By appropriately controlling the reactor temperature, operating the reactor at a temperature lower than MIT 15 in the range defined above effectively prevents such problems.

[0124] In one embodiment, when the slurry polymerization reactor is disposed upstream of the gas phase polymerization reactor, not only can the metallocene catalyst be prevented from being directly exposed to the gas phase polymerization conditions, but the size of the polymer can also be further increased by the slurry polymerization reaction, thereby helping to improve process stability. Furthermore, when a low density prepolymer is prepared in the slurry polymerization reactor, a larger portion of the polymer having the properties of a polyolefin elastomer can be present on the outer surface, disadvantageously causing an increase in the tackiness of the overall polymer and deterioration of process stability.

[0125] In one embodiment, the final polymer can be the polyolefin polymer described above. Specifically, the final polymer includes a core and a shell, wherein the density of the core is 0.857 g / cm 3 to 0.910 g / cm 3 , the density of the shell is 0.890 g / cm 3 to 0.940 g / cm 3 , and the density of the shell is higher than the density of the core.

[0126] The final polymer can exhibit one or more of the following properties (a) through (h). For example, the polyolefin polymer can exhibit two or more or all of the following properties (a) through (h).

[0127] (a) a melt index (MIE, 2.16 kg load, 190°C) of 0.1 g / 10 minutes to 5.0 g / 10 minutes;

[0128] (b) a density of 0.870 g / cm 3 to 0.900 g / cm 3 ;

[0129] (c) two or more melting temperatures (T m );

[0130] (d) a first melting temperature (T m1 ) and a second melting temperature (T m2 ), wherein the difference between T m1 and T m2 is 30°C to 70°C;

[0131] (e) a first melting temperature (T m1 ) of 45°C to 85°C, and a second melting temperature (T m2 ) of 80°C to 125°C;

[0132] (f) two or more crystallization temperatures (T c );

[0133] (g) a first crystallization temperature (T c1 ) of 40°C to 100°C, and a second crystallization temperature (T c2 ) of 70°C to 110°C; and

[0134] (h) two or more peaks in a temperature rising elution fractionation (TREF) chromatogram at temperatures of 35°C or higher, wherein the percent area under the curve at 60°C or higher relative to the total chromatogram area is 5% or greater.

[0135] In one embodiment, the density of the shell (i.e., the prepolymer produced in the slurry polymerization reactor) can be 0.890 g / cm 3 to 0.940 g / cm 3 , 0.895 g / cm 3 to 0.930 g / cm 3 , or 0.900 g / cm 3 to 0.922 g / cm 3 .

[0136] The shell can have a melt index (MIE, 2.16 kg load, 190 °C) of, for example, 0.01 g / 10 min to 5.0 g / 10 min, 0.05 g / 10 min to 3.5 g / 10 min, or 0.05 g / 10 min to 2.0 g / 10 min.

[0137] The shell can have a melting temperature of, for example, 80 °C to 125 °C, 90 °C to 120 °C, or 95 °C to 110 °C.

[0138] In a temperature rising elution fractionation (TREF) chromatogram, the shell can have one peak at a temperature of 60 °C or greater.

[0139] In one embodiment, the density of the core formed within the hollow interior of the prepolymer by the gas phase polymerization reaction can be, for example, 0.857 g / cm 3 to 0.910 g / cm 3 , 0.857 g / cm 3 to 0.900 g / cm 3 , or 0.857 g / cm 3 to 0.898 g / cm 3 .

[0140] The core can have a melting temperature of, for example, 45 °C to 85 °C, 50 °C to 85 °C, or 60 °C to 70 °C.

[0141] The final polymer can have a melt index (MIE, 2.16 kg load, 190 °C) of, for example, 0.1 g / 10 min to 5.0 g / 10 min, 0.5 g / 10 min to 4 g / 10 min, or 0.6 g / 10 min to 3.2 g / 10 min.

[0142] The weight ratio of the core to the shell in the final polymer can be 40:60 to 90:10, 50:50 to 80:20, or 50:50 to 70:30. By forming the core and the shell within these weight ratios, the final polymer can exhibit the low density characteristics of a polyolefin elastomer while minimizing the viscosity and moisture-related stickiness that can impede fluidization, thereby preventing process stability degradation.

[0143] As described above, because the shell and the core have different physical characteristics, a single polyolefin polymer can have two or more melting and crystallization temperatures.

[0144] In one example, the polymerization system can include one slurry polymerization reactor and one gas phase polymerization reactor. In this case, the polymerization system can include a first slurry polymerization reactor 100 configured to slurry polymerize a supplied feed stream in the presence of a catalyst to produce a slurry reaction product comprising a pre-polymer and a first gas phase polymerization reactor 300 configured to receive the slurry reaction product from the first slurry polymerization reactor 100 or the slurry reaction product from the first slurry polymerization reactor 100 and a feed stream and to conduct gas phase polymerization to produce a gas phase reaction product comprising a final polymer.

[0145] In another example, the polymerization system can include one slurry polymerization reactor and two gas phase polymerization reactors. In this case, the polymerization system can include a first slurry polymerization reactor 100 configured to slurry polymerize a supplied feed stream in the presence of a catalyst to produce a slurry reaction product comprising a pre-polymer; a first gas phase polymerization reactor 300 configured to receive the slurry reaction product from the first slurry polymerization reactor 100 or the slurry reaction product from the first slurry polymerization reactor 100 and a feed stream and to conduct gas phase polymerization to produce a first gas phase reaction product comprising a final polymer; and a second gas phase polymerization reactor 400 configured to receive the first gas phase reaction product from the first gas phase polymerization reactor 300 or the first gas phase reaction product from the first gas phase polymerization reactor 300 and a feed stream and to conduct gas phase polymerization to produce a second gas phase reaction product comprising a final polymer.

[0146] In yet another example, the polymerization system can include two slurry polymerization reactors and two gas phase polymerization reactors. In this case, the polymerization system can include a first slurry polymerization reactor 100 configured to slurry polymerize a supplied feed stream in the presence of a catalyst to produce a first slurry reaction product comprising a pre-polymer; a second slurry polymerization reactor 200 configured to receive the first slurry reaction product from the first slurry polymerization reactor 100 or the first slurry reaction product from the first slurry polymerization reactor 100 and a feed stream and to conduct slurry polymerization to produce a second slurry reaction product comprising a pre-polymer; a first gas phase polymerization reactor 300 configured to receive the second slurry reaction product from the second slurry polymerization reactor 200 or the second slurry reaction product from the second slurry polymerization reactor 200 and a feed stream and to conduct gas phase polymerization to produce a first gas phase reaction product comprising a final polymer; and a second gas phase polymerization reactor 400 configured to receive the first gas phase reaction product from the first gas phase polymerization reactor 300 or the first gas phase reaction product from the first gas phase polymerization reactor 300 and a feed stream and to conduct gas phase polymerization to produce a second gas phase reaction product comprising a final polymer.

[0147] In one embodiment, the first gas phase reaction product produced in the first gas phase polymerization reactor 300 can be separated into unreacted gas and polymer by filtration through a filter. The separated polymer can be fed to the second gas phase polymerization reactor 400, and the unreacted gas can be purified in a purification column and recycled to the first slurry polymerization reactor 100 and / or the second slurry polymerization reactor 200.

[0148] Operating a gas phase polymerization reactor at a too low temperature has the disadvantage of significantly reducing the production rate. Furthermore, in the process of producing a polyolefin polymer having a high comonomer content, a local high comonomer ratio can occur when the production rate is increased. As a result, the viscosity of the polymer increases, and an undesired polymer can be produced, causing process problems. In the present disclosure, a method of reducing the viscosity of the polymer under high concentration comonomer conditions using a high adsorption mode is employed.

[0149] As a specific example, the first gas phase polymerization reactor 300 can be operated without a high adsorption mode, and the second gas phase polymerization reactor 400 can be operated in a high adsorption mode. The second gas phase polymerization reactor 400 can be operated such that the injected gas is at a temperature and pressure that condenses it, and the gas discharged from the reactor is at a temperature and pressure that does not condense it.

[0150] For reference, a polyolefin polymerization system can include a circulation line extending from an upper portion of a gas phase polymerization reactor and connected to a lower portion of the gas phase polymerization reactor to circulate a circulation gas stream, a compressor disposed in the circulation line, and a heat exchanger disposed downstream of the compressor based on a flow direction of the circulation gas stream in the circulation line. In the high adsorption mode, an adsorbent can be used in an amount of 0.1 parts by weight to 30 parts by weight, 2 parts by weight to 20 parts by weight, or 3 parts by weight to 15 parts by weight, based on 100 parts by weight of the total circulation gas stream.

[0151] The adsorbent used when the second gas phase polymerization reactor 400 is operated in a high adsorption mode can include propane, isobutane, isopentane, hexane, etc.

[0152] A method of polyolefin polymerization according to one embodiment includes a slurry polymerization step of performing slurry polymerization of a feed composition including a monomer and a comonomer one or more times in the presence of a catalyst to produce a slurry reaction product including a prepolymer, and a gas phase polymerization step of performing gas phase polymerization of the slurry reaction product obtained above or the slurry reaction product and the feed composition one or more times to produce a gas phase reaction product including a final polymer, wherein the reaction temperature of the slurry polymerization step is 20°C to 70°C and higher than the reaction temperature of the gas phase polymerization step, and wherein the final polymer includes a core and a shell having a density higher than that of the core, thus having two or more density distributions.

[0153] The process for the polymerization of polyolefins can be a process for producing a final polymer (i.e., the aforementioned polyolefin polymer) using the aforementioned polyolefin polymerization system.

[0154] In one embodiment, the catalyst can be a metallocene single-site catalyst. The metallocene can be represented by the formula L n MQ p where M is a Group IIIB, IVB, VB, or VIB metal; Q is a hydrocarbyl group or a halogen having 1 to 20 carbon atoms; p is equal to the valence of M minus 2; and L is a ligand bonded to the metal M.

[0155] Such metallocene catalysts are known to be used for producing polyolefins having excellent physical properties due to higher catalytic activity and higher copolymerizability compared to conventional Ziegler-Natta catalysts. The metallocene catalysts can be used as a homogeneous catalyst, and can be supported on a suitable support. For example, the support can be silicon oxide and / or aluminum oxide, and specifically can be silica containing hydroxyl groups or other functional groups containing active hydrogen atoms, and can be in the form of porous spherical particles.

[0156] The metallocene catalyst can be supported on a support together with a cocatalyst, and the cocatalyst can include an alkylaluminoxane. The alkylaluminoxane can include linear and / or cyclic alkylaluminoxane oligomers. When the alkylaluminoxane is a linear alkylaluminoxane oligomer, it can be represented by the formula R-(Al(R)-O) n -AlR2, and when the alkylaluminoxane is a cyclic alkylaluminoxane oligomer, it can be represented by the formula (-Al(R)-O- m where R is a C1-C8 alkyl group, preferably methyl; n is 1 to 40, preferably 10 to 20; and m is 3 to 40, preferably 3 to 20. The alkylaluminoxane is typically a mixture of oligomers having a broad molecular weight distribution and has an average molecular weight of 800 to 1200.

[0157] In one embodiment, the feed stream can include monomers and comonomers.

[0158] The monomer can be ethylene.

[0159] The comonomer can include one or more selected from the group consisting of 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, and 1-octene. In a specific example, the comonomer can include one or more of 1-butene and 1-hexene.

[0160] The feed stream can also include a diluent. The diluent can include one or more of an inert gas and an alkane. The inert gas can include nitrogen, helium, or neon, and the alkane can include butane, propane, isobutane, isopentane, hexane, or isomers thereof. The process can include contacting the catalyst with monomers and comonomers using the diluent in the slurry polymerization reactor and the gas phase polymerization reactor to produce the polyolefin polymer.

[0161] The feed stream including ethylene and comonomer can be polymerized using a system having one or more slurry polymerization reactors and one or more gas phase polymerization reactors sequentially arranged to produce a polyolefin polymer in the presence of a catalyst. In particular examples, the polyolefin polymer can be a polyolefin elastomer, and more particularly, a low density polyethylene.

[0162] In one embodiment, the temperature of the slurry polymerization can be from 20 °C to 70 °C, or from 40 °C to 60 °C. The temperature of the gas phase polymerization can be lower than the temperature of the slurry polymerization, and can be, for example, from 30 °C to 50 °C, or from 35 °C to 48 °C. By conducting each reaction at a reduced temperature to produce the final polymer, viscosity and moisture related sticking that can interfere with fluidization within the reactor can be minimized, further increasing process stability.

[0163] In one embodiment, the pressure of the slurry polymerization can be from 5 K / G to 30 K / G, for example, from 10 K / G to 25 K / G, or from 20 K / G to 25 K / G. The pressure of the gas phase polymerization can be adjusted to be equal to or lower than the pressure of the slurry polymerization. For example, depending on the temperature, the pressure of the gas phase polymerization can be from 10 K / G to 20 K / G, or from 10 K / G to 15 K / G. By operating each reactor at a reduced pressure, viscosity and moisture induced sticking that can interfere with fluidization within the reactor can be minimized, further increasing process stability.

[0164] In one embodiment, by using a multi-stage polymerization of one or more slurry polymerization reactions and one or more gas phase polymerization reactions, a pre-polymer having a relatively high density and a hollow shell structure is produced in the slurry polymerization reaction, and a polyolefin polymer (i.e., a polyolefin elastomer (POE)) is subsequently formed within the hollow interior of the pre-polymer particles in the gas phase polymerization reaction to produce a final polymer. The final polymer can exhibit the properties of a polyolefin elastomer.

[0165] In one embodiment, the molar ratio of ethylene to comonomer alpha-olefin in each reaction can be adjusted to 0.01 to 0.3 depending on the type of comonomer. For example, in a slurry polymerization reaction, the molar ratio of comonomer can be 0.01 to 0.3, 0.05 to 0.3, or 0.07 to 0.27 based on the total amount of monomer and comonomer. In a gas phase polymerization reaction, the molar ratio of comonomer can be 0.01 to 0.2, or 0.05 to 0.18 based on the total amount of monomer and comonomer. By employing different comonomer ratios in each reaction, a polymer having properties such as two or more melting temperatures or two or more crystallization temperatures can be prepared. Such a polymer can have advantages in both processability and physical properties due to high melting temperature and low glass transition temperature (Tg).

[0166] The prepolymer prepared in the slurry polymerization reaction can be present in an amount of 10 to 60 wt% relative to the total amount of the final polymer. For example, the prepolymer can be present in an amount of 20 to 50 wt%, or 30 to 50 wt% relative to the total final polymer. By controlling the weight fraction of the prepolymer within this range, the total density can be increased without impairing the physical properties of the final polymer, while firmly forming a relatively high-density shell. Accordingly, the amount of the polymer prepared in the gas phase polymerization reactor exposed on the outer surface is minimized, thereby improving process stability.

[0167] In one embodiment, the gas phase polymerization reaction can be conducted at a temperature lower than the MIT 15 (15 wt% melting onset temperature) measured according to ASTM 3417-83. Specifically, the temperature lower than the MIT 15 is controlled at a relatively low level to ensure process stability, while establishing a proper temperature range for each reaction. The temperature lower than the MIT 15 may be measured according to ASTM 3417-83 using a DSC instrument by performing a first scan from 25°C to 200°C at a heating rate of 10°C / min and determining the temperature corresponding to 15 wt% melting area percentage.

[0168] For example, the temperature lower than the MIT 15 in the gas phase polymerization reaction can be 40 to 80°C, 40 to 70°C, or 40 to 65°C. When the gas phase polymerization reaction is conducted at a temperature lower than the MIT 15When operated at the same temperature, polymer aggregation can occur, resulting in a decrease in process stability. Meanwhile, a reaction temperature that is too low to ensure process stability can cause a significant decrease in productivity. Furthermore, in a process for preparing a polyolefin polymer having a high comonomer content, as productivity increases, a local region having a high comonomer concentration can be formed, which can increase the viscosity of the polymer and cause the formation of an undesirable polymer, thereby causing a process problem. By appropriately controlling the reaction temperature, operating the reactor at a temperature lower than the MIT 15 defined above within the range defined above effectively prevents such problems.

[0169] In one embodiment, when the slurry polymerization reaction is disposed upstream of the gas phase polymerization reaction, the metallocene catalyst can be prevented from being directly exposed to the gas phase polymerization conditions, and the size of the polymer particles can be increased by the slurry polymerization reaction, thereby contributing to an increase in process stability. On the other hand, when a low-density prepolymer is prepared in the slurry polymerization reaction, a large portion of the polymer having the properties of a polyolefin elastomer can exist on the outer surface, disadvantageously causing an increase in the viscosity of the overall polymer and a deterioration in process stability.

[0170] In one embodiment, the slurry polymerization reaction can provide a prepolymer having a hollow structure to form a shell of the final polymer, and the gas phase polymerization reaction can fill the hollow portion of the prepolymer with a product having a density higher than that of the prepolymer, thereby forming a core of the final polymer.

[0171] Here, the final polymer can be the polyolefin polymer described above. Specifically, a shell having a density of 0.890 g / cm 3 to 0.940 g / cm 3 may be formed by the slurry polymerization step, and a core having a density of 0.857 g / cm 3 to 0.910 g / cm 3 may be formed by the gas phase polymerization step.

[0172] The final polymer can have at least one of the following properties (a) to (h). For example, the polyolefin polymer can have two or more or all of the properties (a) to (h).

[0173] (a) a melt index (MIE, 2.16 kg load, 190°C) of 0.1 g / 10 minutes to 5.0 g / 10 minutes;

[0174] (b) a density of 0.870 g / cm 3 to 0.900 g / cm 3 ;

[0175] (c) two or more melting temperatures (T m );

[0176] (d) First melting temperature (T) m1 ) and second melting temperature (T m2 ), where T m1 With T m2 The difference ranges from 30°C to 70°C;

[0177] (e) The first melting temperature (Tm1) is 45°C to 85°C, and the second melting temperature (Tm1) is... m2 The temperature ranges from 80℃ to 125℃.

[0178] (f) Two or more crystallization temperatures (T) c );

[0179] (g) First crystallization temperature (T) c1 The temperature ranges from 40°C to 100°C, and the second crystallization temperature (T) is... c2 The temperature ranges from 70°C to 110°C; and

[0180] (h) The temperature-elution fractionation (TREF) chromatogram has two or more peaks at 35°C or higher, wherein the area of ​​the peaks at 60°C or higher accounts for 5% or more of the total chromatogram area.

[0181] In one embodiment, the shell (i.e., the prepolymer prepared in the slurry polymerization reactor) may have a content of 0.890 g / cm³. 3 Up to 0.940 g / cm 3 0.895 g / cm 3 Up to 0.930 g / cm 3 or 0.900 g / cm 3 Up to 0.922 g / cm 3 The density.

[0182] The shell may have a melt index (MIE, 2.16 kg load, 190°C) of, for example, 0.01 g / 10 min to 5.0 g / 10 min, 0.05 g / 10 min to 3.5 g / 10 min, or 0.05 g / 10 min to 2.0 g / 10 min.

[0183] The shell may have a melting temperature of, for example, 80°C to 125°C, 90°C to 120°C, or 95°C to 110°C.

[0184] In a temperature-elution fractionation (TREF) chromatogram, the shell may have a peak at a temperature of 60°C or higher.

[0185] In one embodiment, the density of the cores formed within the hollow interior of the prepolymer via gas-phase polymerization can be, for example, 0.857 g / cm³.3 to 0.910 g / cm 3 , 0.855 g / cm 3 to 0.900 g / cm 3 , or 0.857 g / cm 3 to 0.898 g / cm 3 .

[0186] The core can have a melting temperature of, for example, 45°C to 85°C, 50°C to 85°C, or 60°C to 70°C.

[0187] The final polymer can have a melt index (MIE, 2.16 kg load, 190°C) of, for example, 0.1 g / 10 minutes to 5.0 g / 10 minutes, 0.5 g / 10 minutes to 4 g / 10 minutes, or 0.6 g / 10 minutes to 3.2 g / 10 minutes. The weight ratio of the core to the shell in the final polymer can be 40:60 to 90:10, 50:50 to 80:20, or 50:50 to 70:30. By forming the core and the shell within these weight ratios, the final polymer can exhibit the low density characteristics of a polyolefin elastomer while minimizing the viscosity and moisture-related adhesion that can impede fluidization, thereby preventing deterioration of process stability.

[0188] As described above, since the shell and the core have different physical characteristics, characteristics such as two or more melting temperatures and two or more crystallization temperatures can occur in a single polyolefin polymer.

[0189] As one example, a method of polyolefin polymerization can include a slurry polymerization step of slurry polymerizing a feed composition including a monomer and a comonomer in the presence of a catalyst to prepare a slurry reaction product including a prepolymer, and a gas phase polymerization step of gas phase polymerizing the slurry reaction product obtained above or the slurry reaction product and the feed composition to prepare a final polymer.

[0190] Figure 2a A method of polyolefin polymerization according to one embodiment is illustrated. Specifically, referring to Figure 2a , the polyolefin polymerization method can include sequentially performing a slurry polymerization reaction and a gas phase polymerization reaction.

[0191] As another example, a process for polyolefin polymerization can include a first slurry polymerization step of slurry polymerizing a feed composition comprising monomers and comonomers in the presence of a catalyst to produce a first slurry reaction product comprising a prepolymer; a first gas phase polymerization step of gas phase polymerizing the above obtained first slurry reaction product or the first slurry reaction product and the feed composition to produce a first gas phase reaction product comprising a final polymer; and a second gas phase polymerization step of gas phase polymerizing the above obtained first gas phase reaction product or the first gas phase reaction product and the feed composition to produce a second gas phase reaction product comprising a final polymer.

[0192] As another example, a process for polyolefin polymerization can include a first slurry polymerization step of slurry polymerizing a feed composition comprising monomers and comonomers in the presence of a catalyst to produce a first slurry reaction product comprising a prepolymer; a first gas phase polymerization step of gas phase polymerizing the above obtained first slurry reaction product or the first slurry reaction product and the feed composition to produce a first gas phase reaction product comprising a final polymer; and a second gas phase polymerization step of gas phase polymerizing the above obtained first gas phase reaction product or the first gas phase reaction product and the feed composition to produce a second gas phase reaction product comprising a final polymer.

[0193] Figure 2d A process for polyolefin polymerization according to one embodiment is shown. Specifically, referring to Figure 2d , a polyolefin polymerization process can sequentially include a first slurry polymerization reaction, a second slurry polymerization reaction, a first gas phase polymerization reaction, and a second gas phase polymerization reaction.

[0194] In one embodiment, the first gas phase reaction product produced in the first gas phase polymerization reaction can be separated into unreacted gas and polymer by filtration through a filter. The separated polymer can be used to conduct the second gas phase polymerization reaction, and the unreacted gas can be recycled and reused in the first slurry polymerization reaction and / or the second slurry polymerization reaction.

[0195] Operating a gas phase polymerization reaction at too low a temperature has the disadvantage of significantly reducing the production rate. Furthermore, during the production of polyolefin polymers with high comonomer content, an increase in the production rate can locally cause a high comonomer concentration, thereby increasing the viscosity of the polymer and causing agglomeration or the formation of undesirable polymer, which can cause process problems. Therefore, in the present disclosure, a high adsorption mode is applied to reduce the polymer viscosity under high comonomer concentration conditions.

[0196] As a specific example, the first gas phase polymerization reaction can be conducted without a high adsorption mode, and the second gas phase polymerization reaction can be conducted with a high adsorption mode. The second gas phase polymerization reaction can be conducted such that the injected gas is at a temperature and pressure that causes it to condense, and the gas that exits the reactor is at a temperature and pressure that does not cause it to condense.

[0197] For reference, the gas phase polymerization reaction can be conducted using a circulation line that extends from an upper portion of the gas phase polymerization reactor and is connected to a lower portion of the gas phase polymerization reactor to circulate a circulation gas stream, a compressor disposed in the circulation line, and a heat exchanger disposed downstream of the compressor based on a flow direction of the circulation gas stream in the circulation line. In the high adsorption mode, the adsorbent can be used in an amount of 0.1 parts by weight to 30 parts by weight, 2 parts by weight to 20 parts by weight, or 3 parts by weight to 15 parts by weight, based on 100 parts by weight of the total circulation gas stream.

[0198] The adsorbent used when operating the second gas phase polymerization reaction in the high adsorption mode can include propane, isobutane, isopentane, hexane, etc.

[0199] When the polyolefin polymerization is conducted by a method including two slurry polymerization steps and two gas phase polymerization steps, the two slurry polymerization steps can provide a shell having a density of 0.890 g / cm 3 to 0.940 g / cm 3 , the first gas phase polymerization step can provide a core having a density of 0.887 g / cm 3 to 0.898 g / cm 3 , and the second gas phase polymerization step can provide a core having a density of 0.857 g / cm 3 to 0.886 g / cm 3 .

[0200] The shell can have a density of, for example, 0.890 g / cm 3 to 0.940 g / cm 3 , 0.895 g / cm 3 to 0.930 g / cm 3 , or 0.900 g / cm 3 to 0.922 g / cm 3 , through the two slurry polymerization steps.

[0201] The core can have a density of 0.887 g / cm 3 to 0.898 g / cm 3 , or 0.888 g / cm 3 to 0.897 g / cm 3 , through the first gas phase polymerization step.

[0202] The core can have a density of 0.857 g / cm 3 to 0.886 g / cm 3 , or 0.857 g / cm 3 to 0.884 g / cm 3 .

[0203] As described above, the polyolefin polymer can be prepared by forming a relatively high density shell through a slurry polymerization reaction, a core having a lower density than the density formed in the slurry polymerization reaction through a first gas phase polymerization reaction, and a core having an even lower density than the density formed in the first gas phase polymerization reaction through a second gas phase polymerization reaction. Such a density gradient enables the catalyst to prepare a prepolymer having a relatively high density in the slurry polymerization reaction compared to the gas phase polymerization reaction, thereby improving process stability when performing the subsequent first gas phase polymerization reaction and second gas phase polymerization reaction. Due to the density gradient, the prepared polyolefin polymer can exhibit a high melting temperature and a low melting temperature (i.e., two or more melting temperatures), and can also have a low glass transition temperature. Due to these properties of the polyolefin polymer, the rotational speed during molding can be increased, thereby improving process productivity, and physical properties such as resilience are improved due to the low glass transition temperature.

[0204] Hereinafter, specific embodiments of the present disclosure will be described. However, the following described embodiments are provided only for the purpose of illustration or explanation of the present disclosure, and the scope of the present disclosure should not be construed as being limited thereto. In addition, matters not specifically described herein can be well understood and technically inferred by those skilled in the art, and thus a detailed description thereof is omitted.

[0205] (Preparation of polyolefin polymer)

[0206] Examples 1 to 4 and Comparative Examples 1 and 2

[0207] A polyolefin polymer (specifically, linear low density polyethylene) was produced using one slurry polymerization reactor and one gas phase polymerization reactor. The operating conditions of each reactor are shown in Table 1 below.

[0208] The polymerization reaction was performed by simulating the conditions of the slurry polymerization reaction and the gas phase polymerization reaction in a batch polymerization reactor using a catalyst composition prepared by combining a metallocene catalyst, methylaluminoxane (MAO), and a porous support.

[0209] In order to adjust the polymerization temperature, a 2L stainless steel autoclave reactor equipped with a jacket capable of supplying external cooling water was heated from room temperature to 110°C, purged with nitrogen, and purged using 400 ml of isobutane.

[0210] After adjusting the temperature, 1.5 ml of 0.2 M triethylaluminum (TEAL), 2.5 ml (1.1 mmol in hexane) of the antistatic agent (Statsafe® 6000 from Innospec Inc.), and 1 L of isobutane were charged into the reactor.

[0211] Thereafter, ethylene, 1-hexene (wt%, 1-hexene charge amount relative to the ethylene charged), and hydrogen (mg / kg C2, hydrogen charge amount (mg) relative to 1 kg of ethylene charged) were charged, and the loaded catalyst was charged into the reactor. The slurry polymerization reaction was performed according to the polymerization conditions shown in Table 1 below. During the slurry polymerization, the ethylene partial pressure was kept constant, and 1-hexene and hydrogen were continuously charged together with ethylene. After the completion of the slurry polymerization, unreacted 1-hexene and isobutane were discharged.

[0212] For the gas phase polymerization reaction, nitrogen gas was injected into the gas phase polymerization reactor as a diluent at 100 psi, 250 ppm of the antistatic agent was injected, and the temperature was adjusted to 48°C.

[0213] After adjusting the temperature, the gas phase polymerization reaction was performed according to the polymerization conditions shown in Table 1 below. After the completion of the reaction, unreacted gas was discharged, the reactor was opened to obtain a linear low density polyethylene (LLDPE) resin having fluidity as a final polymer, and its physical properties were measured, the results of which are shown below.

[0214] [Table 1]

[0215]

[0216] 1) MIE in the gas phase polymerization reactor is a measured value of the final polymer.

[0217] The measurement methods of each of the physical properties in Table 1 above and Table 2 below are shown below.

[0218] Melt flow index (MIE, MI2.16): measured according to ASTM D1238 at 190°C and a load of 2.16 kg.

[0219] High load melt flow index (MIF, MI21.6): measured according to ASTM D1238 at 190°C and a load of 21.6 kg.

[0220] Melt flow rate ratio (SR, MFRR): calculated as MIF / MIE (F / E).

[0221] Density: measured according to ASTM D1505 using the density gradient method.

[0222] B.D: is the bulk density (apparent density) and is measured according to ASTM D1895.

[0223] Molecular weight and molecular weight distribution: measured as follows using a gel permeation chromatography (GPC) device equipped with a refractive index detector (RI detector) (GPC-RI; 220 system from Polymer Laboratory Inc.). Two Olexis columns and one guard column were used as separation columns, the column temperature was maintained at 160 °C. Calibration was performed using a standard polystyrene kit from Polymer Laboratory Inc. A 27 minute measurement was performed using trichlorobenzene containing 0.0125 wt% antioxidant (BHT) as eluent, a sample concentration of 1.0 mg / ml, at an injection volume of 0.2 ml, a pump flow of 1.0 ml / min. The number average molecular weight (Mn), the weight average molecular weight (Mw) and the Z average molecular weight (Mz) were calculated after universal calibration using polystyrene standard materials Easical A and Easical B (from Agilent Technologies) and their conversion to polyethylene.

[0224] Melting temperature (T m ) and crystallization temperature (T c ): measured according to ASTM 3417-83 using a DSC device and using the values shown in the second scan at a temperature range from 25 °C to 200 °C at 10 °C / min.

[0225] Glass transition temperature (T g ): measured according to ASTM 3417-83 using a DSC device and using the values shown in the second scan at a temperature range from -80 °C to 200 °C at 40 °C / min.

[0226] MIT 15 : measured according to ASTM 3417-83 using a DSC device and based on the area where 15 wt% of the melting area percentage occurs in the first scan at a temperature range from 25 °C to 200 °C at 10 °C / min.

[0227] Comonomer (wt%): analyzed and calculated by 13C NMR according to ASTM D5017.

[0228] Temperature Rising Elution Fractionation (TREF): Analysis was performed using a cross-fractionation chromatography (CFC) (PolymerChar CFC-2) instrument as follows. Two Olexis columns and one guard column were used as separation columns, and the column temperature was maintained at 150 °C, using a standard polystyrene kit from Polymer Laboratory Inc. for calibration. Trichlorobenzene containing 0.0125 wt% antioxidant (BHT) was used as eluent, the sample concentration was 75 mg / mL, and the pump flow rate was 1.0 mL / min. After injection of the sample, the oven and sample temperature were raised to 150 °C at a heating rate of 40 °C / min, maintained at 150 °C for 60 min, and then cooled to 95 °C at a cooling rate of 40 °C / min. After the sample was maintained at 95 °C for 45 min, it was again cooled to 30 °C at a cooling rate of 0.5 °C / min and maintained for 30 min. Thereafter, while the temperature of the sample was raised from 35 °C to 120 °C, the fractions according to temperature were divided into 22 portions at intervals of 4 °C, 0.5 mL of the sample was injected into each fraction, and the eluted fractions were passed through the TREF column and the Olexis column to obtain TREF values and molecular weights simultaneously. The molecular weights were calculated after universal calibration using polystyrene standard materials Easical A and Easical B (from Agilent Technologies) and converting them to polyethylene. Data processing was performed using “CFCCalibration” (an analysis program attached to the instrument), and the analysis took about 600 min. An infrared spectrometer was used as a detector.

[0229] Independent density: was calculated using Equation 1 below.

[0230] [Equation 1]

[0231]

[0232] In Equation 1, d is the density of the final polymer, d1 and m1 are the independent density and fraction (wt%) of the polymer produced in the first slurry polymerization reactor, respectively, d2 and m2 are the independent density and fraction (wt%) of the polymer produced in the second slurry polymerization reactor, respectively, d3 and m3 are the independent density and fraction (wt%) of the polymer produced in the first gas phase polymerization reactor, respectively, d4 and m4 are the independent density and fraction (wt%) of the polymer produced in the second gas phase polymerization reactor, respectively, and m1+m2+m3+m4=1.

[0233] Here, for Examples 1 to 4 and Comparative Examples 1 and 2 using one slurry polymerization reactor and one gas phase polymerization reactor, it is assumed that a first slurry polymerization reactor and a second gas phase polymerization reactor are used, and factors related to a second slurry polymerization reactor and a first gas phase polymerization reactor are excluded from the equations before calculation.

[0234] Examples 5 to 7 and Comparative Example 3

[0235] Polyolefin polymers (specifically, linear low density polyethylene) were produced using a catalyst composition (M-Cat') prepared by combining a metallocene catalyst, methylaluminoxane (MAO), and a porous support using two slurry polymerization reactors and two gas phase polymerization reactors. The operating conditions of each reactor are shown in Table 2 below.

[0236] The fluidized bed of the first slurry polymerization reactor and the second slurry polymerization reactor was composed of polymer particle granules. 1-butene, ethylene, and hydrogen were mixed in a pipe, injected into a circulation line, and the composition of the injected and the physical properties of the produced prepolymer are listed in Table 2 below.

[0237] The concentration of ethylene, hydrogen, and 1-butene injected into the first gas phase polymerization reactor and the second gas phase polymerization reactor was adjusted to maintain the composition listed in Table 2 below. In addition, the prepolymer was supplied in an amount of 5 to 10% by weight of the total weight of the polymerization composition (prepolymer + ethylene + 1-butene), and in the component concentration of the first gas phase polymerization reactor and the second gas phase polymerization reactor in Table 2 below, the remaining amount in mole percentage other than ethylene, hydrogen, and 1-butene refers to propane as a diluent.

[0238] The concentration of all gases was measured by online gas chromatography of the gases in the circulation gas stream. The reaction product discharged from the first gas phase polymerization reactor was separated by a filter that separates unreacted gases from the polymer, and then the polymer was transferred to the second gas phase polymerization reactor, and the separated unreacted gases were passed through a purification column and injected into the first slurry polymerization reactor. The slurry polymerization reactor and the gas phase polymerization reactor used propane as a diluent, and the copolymer of ethylene and 1-butene produced by the catalytic reaction was continuously discharged and transported so that the height of the fluidized bed of the gas phase polymerization reactor was maintained constant. In order to maintain the operating temperature constant, the heat generated by the polymerization was removed by controlling the temperature of the circulation gas using a heat exchanger.

[0239] Thereafter, the reaction product was discharged from the second gas phase polymerization reactor, degassed and dried to obtain a linear low density polyethylene (LLDPE) resin as a final polymer, and the physical properties thereof were measured, and the results are shown in Table 2.

[0240] [Table 2]

[0241]

[0242] 1) MIE in the second gas phase polymerization reactor is measured value for the final polymer.

[0243] In Table 2, the comonomer is 1-butene, and the comonomer mole ratio is the mole ratio of 1-butene to the total amount of ethylene and 1-butene.

[0244] (Experimental Example)

[0245] Experimental Example 1: Determination of the structure of the polyolefin polymer

[0246] 1. Cross-section of the prepolymer

[0247] A cross-section of the prepolymer contained in the reaction product produced in the slurry polymerization reactor in Example 2 was photographed using a scanning electron microscope (SEM), and the image is shown in Figure 4a .

[0248] Referring to Figure 4a , it can be seen that the prepolymer having a hollow structure is produced by the slurry polymerization reaction, thereby forming a shell of the final polymer.

[0249] 2. Cross-section of the final polymer

[0250] A cross-section of the final polymer contained in the reaction product produced in the gas phase polymerization reactor in Example 2 was photographed using a scanning electron microscope (SEM), and the image is shown in Figure 4b . In addition, the densities of the shell and the core are shown on the image.

[0251] Referring to Figure 4b , it can be seen that the core having a relatively low density is formed in the hollow prepolymer by the gas phase polymerization reaction.

[0252] 3. Cross-section of the final polymer before and after dissolution in xylene

[0253] A cross-section of the final polymer contained in the reaction product produced in the gas phase polymerization reactor in Example 2 and a cross-section of the final polymer after the final polymer is dissolved in a xylene solution were photographed using a scanning electron microscope (SEM), and the images are shown in Figure 4c . Specifically, Figure 4c the left image in is an image photographed before the final polymer is dissolved in a xylene solution, and the right image is an image photographed after the final polymer is dissolved in a xylene solution.

[0254] The above xylene dissolution experiment is an experiment in which a portion having a low density and a high MI is partially dissolved and eluted in xylene, as shown in Figure 4cAs shown, when the final polymer is dissolved in xylene, it can be seen that only the core having a relatively low density is dissolved, and the shell having a high density of 0.916 remains undissolved. Thus, it can be determined that the final polymer according to the present disclosure has a core-shell structure in which a core having a low density is formed inside, and a shell having a high density and surrounding the core is formed outside.

[0255] Experimental Example 2: Determination of polyolefin polymer by TREF

[0256] For the final polymers produced in Examples 1 to 7 and Comparative Example 3, the TREF values according to temperature were measured by the above-described method to obtain a temperature rising elution fractionation (TREF) chromatogram, which can be determined by Table 1 and Table 2. In addition, Figure 5 The obtained temperature rising elution fractionation (TREF) chromatogram of the final polymer produced in Example 5 and Comparative Example 3 is shown.

[0257] Referring to Table 1 and Table 2, and Figure 5 It can be seen that the final polymers according to Examples 1 to 7 show two peaks at a temperature of 35°C or higher, and have a percentage value of 5% or more obtained by dividing the area under the graph higher than 60°C by the total area under the graph. On the other hand, it can be seen that the final polymer according to Comparative Example 3 shows one peak at a temperature of 35°C or higher, and has a percentage value of 3% obtained by dividing the area under the graph higher than 60°C by the total area under the graph.

[0258] [Reference Signs]

[0259] 100: first slurry polymerization reactor

[0260] 110: catalyst feed

[0261] 120: feed stream feed

[0262] 130: circulation pump

[0263] 140: heat exchanger

[0264] 150: polymer discharge

[0265] 151: first prepolymer discharge

[0266] 200: second slurry polymerization reactor

[0267] 210: first prepolymer feed

[0268] 220: feed stream feed

[0269] 230: circulation pump

[0270] 240: heat exchanger

[0271] 250: second prepolymer discharge

[0272] 300: first gas phase polymerization reactor

[0273] 310: prepolymer feed

[0274] 320: feed stream feed

[0275] 330: compressor

[0276] 340: heat exchanger

[0277] 350: feed stream feed

[0278] 360: first final polymer discharge

[0279] 400: second gas phase polymerization reactor

[0280] 410: first final polymer feed

[0281] 420: feed stream feed

[0282] 430: compressor

[0283] 440: heat exchanger

[0284] 450: feed stream feed

[0285] 460: second final polymer discharge

Claims

1. A polyolefin polymerization system, comprising: One or more slurry polymerization reactors, said slurry polymerization reactors being configured to slurry polymerize a supplied feed stream in the presence of a catalyst to prepare a slurry reaction product comprising a prepolymer. The feed stream comprises monomers and comonomers, and Each slurry polymerization reactor includes: A loop including one or more reactors; One or more polymer outlets; One or more single-unit inlets; One or more heat exchangers; and One or more circulating pumps.

2. The polyolefin polymerization system according to claim 1, wherein a shell is formed by the slurry polymerization reactor.

3. The polyolefin polymerization system according to claim 1, wherein the heat exchanger is a shell-and-tube type.

4. The polyolefin polymerization system according to claim 3, wherein the heat exchanger has a cooling water flow rate of 1 m / s or greater, preferably 3 m / s or greater, and 0.3 Mcal / m 2 ×hr×K or greater, preferably 0.6 megacal / m 2 ×hr×K or greater heat transfer efficiency.

5. The polyolefin polymerization system according to claim 1, further comprising: One or more gas-phase polymerization reactors, the one or more gas-phase polymerization reactors being configured to receive the slurry reaction product or the slurry reaction product and the feed stream, and to gas-phase polymerize the slurry reaction product or the slurry reaction product and the feed stream to prepare a gas-phase reaction product comprising a final polymer.

6. The polyolefin polymerization system according to claim 5, wherein the nucleus is formed through the gas-phase polymerization reactor.

7. The polyolefin polymerization system of claim 5, wherein the final polymer comprises a core and a shell with a density higher than that of the core to provide two or more density distributions, and The operating temperature of the slurry polymerization reactor is 20°C to 70°C, which is higher than the operating temperature of the gas-phase polymerization reactor.

8. The polyolefin polymerization system according to claim 7, wherein the density of the core is 0.857 g / cm³. 3 Up to 0.910 g / cm 3 The density of the shell is 0.890 g / cm³. 3 Up to 0.940 g / cm 3 ,and The density of the shell is higher than the density of the core.

9. The polyolefin polymerization system according to claim 7, wherein the final polymer has at least one of the following properties (a) to (h): (a) Melt index of 0.1 g / 10 min to 5.0 g / 10 min (MIE, 2.16 kg load, 190 °C). (b) Density is 0.870 g / cm³ 3 Up to 0.900 g / cm 3 ; (c) Two or more melting temperatures (T) m ); (d) First melting temperature (T) m1 ) and second melting temperature (T m2 ), where T m1 With T m2 The difference ranges from 30°C to 70°C; (e) First melting temperature (T) m1 The temperature ranges from 45°C to 85°C, and the second melting temperature (T) is... m2 The temperature ranges from 80℃ to 125℃. (f) Two or more crystallization temperatures (T) c ); (g) First crystallization temperature (T) c1 The temperature ranges from 40°C to 100°C, and the second crystallization temperature (T) is... c2 The temperature ranges from 70°C to 110°C; and (h) The temperature-elution fractionation (TREF) chromatogram has two or more peaks at 35°C or higher, wherein the area of ​​the peaks at 60°C or higher accounts for 5% or more of the total chromatogram area.

10. The polyolefin polymerization system according to claim 5, comprising: A first slurry polymerization reactor is configured to slurry polymerize a supplied feed stream in the presence of a catalyst to prepare a slurry reaction product comprising a prepolymer. as well as A first gas-phase polymerization reactor is configured to receive the slurry reaction product or the slurry reaction product and the feed stream, and to perform gas-phase polymerization of the slurry reaction product or the slurry reaction product and the feed stream to prepare a gas-phase reaction product comprising a final polymer.

11. The polyolefin polymerization system according to claim 5, comprising: A first slurry polymerization reactor is configured to slurry polymerize a supplied feed stream in the presence of a catalyst to prepare a first slurry reaction product comprising a prepolymer. A second slurry polymerization reactor is configured to receive the first slurry reaction product from the first slurry polymerization reactor or the first slurry reaction product and feed stream from the first slurry polymerization reactor, and to slurry polymerize the first slurry reaction product or the first slurry reaction product and the feed stream to prepare a second slurry reaction product comprising a prepolymer. A first gas-phase polymerization reactor is configured to receive a second slurry reaction product from a second slurry polymerization reactor or a second slurry reaction product from a second slurry polymerization reactor and a feed stream, and to gas-phase polymerize the second slurry reaction product or the second slurry reaction product and the feed stream to prepare a first gas-phase reaction product comprising a final polymer. as well as A second gas-phase polymerization reactor is configured to receive the first gas-phase reaction product from the first gas-phase polymerization reactor or the first gas-phase reaction product and feed stream from the first gas-phase polymerization reactor, and to gas-phase polymerize the first gas-phase reaction product or the first gas-phase reaction product and the feed stream to prepare a second gas-phase reaction product comprising a final polymer.

12. The polyolefin polymerization system according to claim 1, wherein the catalyst is a metallocene single-site catalyst.

13. The polyolefin polymerization system according to claim 1, wherein the monomer is ethylene.

14. The polyolefin polymerization system of claim 1, wherein the comonomer comprises one or more selected from 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, and 1-octene.

15. The polyolefin polymerization system according to claim 7, wherein the slurry polymerization reactor operates at a temperature of 40°C to 60°C, and the gas-phase polymerization reactor operates at a temperature of 30°C to 50°C.

16. The polyolefin polymerization system of claim 7, wherein the gas-phase polymerization reactor operates at a temperature below the MIT measured according to ASTM 3417-83. 15 It operates at a temperature of (15% by weight melting start temperature).

17. The polyolefin polymerization system of claim 11, wherein the second gas-phase polymerization reactor is operated in a high-adsorption mode, and in the high-adsorption mode, an adsorbent is used in an amount of 0.1 parts by weight to 30 parts by weight based on 100 parts by weight of circulating gas flow.

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