Polyolefin polymer, and polyolefin polymerization system and polymerization method

Abstract

To provide: a low-density polyolefin polymer including a core portion and a shell portion and having a density distribution in which the density of the shell portion is higher than that of the core portion; and a polymerization system and a polymerization method thereof.SOLUTION: A polyolefin polymer includes a core portion and a shell portion, where the core portion has a density of 0.857 g / cm3 to 0.910 g / cm3, the shell portion has a density of 0.890 g / cm3 to 0.940 g / cm3, and the density of the shell portion is higher than that of the core portion. A polymerization system includes: one or more slurry polymerization reactors that produce a slurry reaction product including a prepolymer through slurry polymerization reaction of a feed stream supplied in the presence of a catalyst; and one or more gas phase polymerization reactors that are supplied with the slurry reaction product and produce a gas phase reaction product including a final polymer through gas phase polymerization reaction of the slurry reaction product. The operating temperature of the slurry polymerization reactors is 20°C to 70°C, which is higher than the operating temperature of the gas phase polymerization reactors.SELECTED DRAWING: Figure 1a

Description

[Technical field]

[0001] The present invention relates to polyolefin polymers, polyolefin polymerization systems and methods. [Background technology]

[0002] Linear low-density polyethylene (LLDPE) is widely produced through a gas phase process using a fluidized bed reactor. Specifically, it is produced by copolymerizing ethylene monomer and a comonomer in the presence of a catalyst.

[0003] Here, when producing a polymer such as linear low density polyethylene, a comonomer having a carbon number of 4 or more is used compared to ethylene monomer. The comonomer has a low vapor pressure and is condensed in the polymerization reactor and absorbed into the polymer, causing the polymer to swell. A polymer containing a large amount of comonomer has a low crystallinity and a low melting point, and becomes a sticky wettable resin in the polymerization reactor. Such sticky polymers hinder fluidization in the reactor due to their stickiness, and have a negative effect on the continuous operation of the gas phase polymerization reactor.

[0004] U.S. Patent Publication 4,994,534 describes a process for adding silica, clay, etc., during polymerization to produce sticky polymers, such as ethylene / propylene rubber. The addition of such materials to the reactor not only produces polymers that are unusable in many applications, but can also cause fouling of heat exchangers, compressors, and other reactor systems.

[0005] Similarly, U.S. Patent Publication No. 4,970,279 and International Publication No. WO88 / 02379 described a method of adding ground inorganic materials such as silica or alumina to a reactor. U.S. Patent Publication Nos. 5,100,979 and 5,106,926 described a process for producing ethylene / 1-octene copolymers using a specific titanium-based catalyst system or a specific vanadium-based catalyst system not used commercially. U.S. Patent Publication No. 5,017,665 described a process for producing ethylene / 1-butene / 1,4-hexadiene under a metallocene / aluminoxane catalyst system to produce a polymer having a very low molecular weight and low density. U.S. Patent Publication No. 5,712,353 described a process for producing a relatively high molecular weight and low density elastomer using a metallocene catalyst. This method produces elastomers with high molecular weight and low density at temperatures of 50°C or higher. However, due to the characteristics of elastomers, which have a low melting point and are sticky, there is a high possibility that process problems will occur that make continuous operation difficult when produced at high temperatures. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent Publication No. 4,994,534 [Patent Document 2] U.S. Patent Publication No. 4,970,279 [Patent Document 3] International Patent Publication WO88 / 02379 [Patent Document 4] U.S. Patent Publication No. 5,100,979 [Patent Document 5] U.S. Patent Publication No. 5,106,926 [Patent Document 6] U.S. Patent Publication No. 5,017,665 [Patent Document 7] U.S. Patent Publication No. 5,712,353 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a low-density polyolefin polymer that includes a core portion and a shell portion and has a density distribution in which the density of the shell portion is higher than the density of the core portion, and a polymerization system and method thereof, thereby preventing problems in which continuous operation is difficult and process stability is reduced due to stickiness when the surface of a polymer has a low density. [Means for solving the problem]

[0008] One embodiment includes a core and a shell, and the core has a density of 0.857 g / cm 3 ~0.910g / cm 3 and the density of the shell portion is 0.890 g / cm 3 ~0.940g / cm 3 and the density of the shell portion is higher than the density of the core portion.

[0009] The polyolefin polymer may have one or more of the following physical properties (a) to (h). (a) Melt flow index (MIE) from 0.1g / 10min to 5.0g / 10min (2.16kg load, 190℃) (b) 0.870 g / cm 3 ~0.900g / cm 3 Density of (c) Two or more melting temperatures (T m ) (d) First melting temperature (T m1 ) and the second melting temperature (T m2 ) and the difference between the first melting temperature and the second melting temperature is 30°C to 70°C. (e) First melting temperature (T m1 ) and the second melting temperature (T m2 ), the first melting temperature is 45°C to 85°C, and the second melting temperature is 80°C to 125°C. (f) Two or more crystallization temperatures (T c ) (g) First crystallization temperature (T c1) and the second crystallization temperature (T c2 ), the first crystallization temperature is 40°C to 100°C, and the second crystallization temperature is 70°C to 110°C. (h) In a temperature rising elution fractionation (TREF) chromatogram, two or more peaks are shown at temperatures of 35°C or higher, and the percentage value obtained by dividing the graph area above 60°C by the total graph area is 5% or higher.

[0010] The core has a density of 0.857 g / cm 3 ~0.910g / cm 3 The melting temperature is 45°C to 85°C, and the shell has a melt flow index (MIE (2.16 kg load, 190°C)) of 0.01 g / 10 min to 5.0 g / 10 min and a density of 0.890 g / cm 3 ~0.940g / cm 3 The polymer has a melting temperature of 80°C to 125°C and exhibits one peak at a temperature of 60°C or higher in a temperature rising elution fractionation (TREF) chromatogram, and the weight ratio of the core part to the shell part may be 40:60 to 90:10.

[0011] Another embodiment provides a polyolefin polymerization system, comprising: one or more slurry polymerization reactors for slurry polymerizing a feedstream in the presence of a catalyst to produce a slurry reaction product including a prepolymer; and one or more gas-phase polymerization reactors for receiving the slurry reaction product or the slurry reaction product and a feedstream and gas-phase polymerizing the slurry reaction product to produce a gas-phase reaction product including a final polymer, wherein the feedstream comprises a monomer and a comonomer, the final polymer comprises a core portion and a shell portion having a higher density than the core portion, and has 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.

[0012] The polyolefin polymerization system may include a first slurry polymerization reactor that performs a slurry polymerization reaction of a feed stream supplied thereto in the presence of a catalyst to produce a slurry reaction product including a prepolymer, and a second gas-phase polymerization reactor that receives the slurry reaction product, or the slurry reaction product and a feed stream, and performs a gas-phase polymerization reaction therein to produce a gas-phase reaction product including a final polymer.

[0013] The polyolefin polymerization system may include a first slurry polymerization reactor that performs a slurry polymerization reaction of a feed stream supplied in the presence of a catalyst to produce a first slurry reaction product including a prepolymer; a second slurry polymerization reactor that receives the first slurry reaction product or the first slurry reaction product and a feed stream from the first slurry polymerization reactor and performs a slurry polymerization reaction to produce a second slurry reaction product including a prepolymer; a first gas-phase polymerization reactor that receives the second slurry reaction product or the second slurry reaction product and a feed stream from the second slurry polymerization reactor and performs a gas-phase polymerization reaction to produce a first gas-phase reaction product including a final polymer; and a second gas-phase polymerization reactor that receives the first gas-phase reaction product or the first gas-phase reaction product and a feed stream from the first gas-phase polymerization reactor and performs a gas-phase polymerization reaction to produce a second gas-phase reaction product including a final polymer.

[0014] The catalyst may be a metallocene monocatalyst. The monomer may be ethylene. The comonomer may be any one or more selected from the group consisting of 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, and 1-octene.

[0015] The operating temperature of the slurry polymerization reactor may be 40°C to 60°C, and the operating temperature of the gas phase polymerization reactor may be 30°C to 50°C. The gas phase polymerization reactor had an MIT 15It can be operated at temperatures below (15 wt % melting initiation temperature).

[0016] The second gas phase polymerization reactor is operated in a high sorption mode, in which the sorbent can be used in an amount of 0.1 to 30 parts by weight per 100 parts by weight of the total recycle gas stream.

[0017] In still another embodiment, there is provided a method for polymerizing polyolefins, comprising: a slurry polymerization step of slurry-polymerizing a feed composition including a monomer and a comonomer in the presence of a catalyst at least once to produce a slurry reaction product including a prepolymer; and a gas-phase polymerization step of gas-phase polymerizing the slurry reaction product obtained in the above step or the slurry reaction product and a feed composition at least once 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, which is higher than the reaction temperature of the gas-phase polymerization step, and the final polymer has two or more density distributions including a core portion and a shell portion having a higher density than the core portion.

[0018] The polyolefin polymerization method may include a slurry polymerization step of slurry polymerizing a feed composition including a monomer and a comonomer in the presence of the catalyst to produce a slurry reaction product including a prepolymer, and a gas phase polymerization step of gas phase polymerizing the slurry reaction product obtained in the above step or the slurry reaction product and a feed composition to produce a final polymer.

[0019] The polyolefin polymerization method may include a first slurry polymerization step of performing a primary slurry polymerization reaction of a feed composition including a monomer and a comonomer in the presence of a catalyst to produce a first slurry reaction product including a prepolymer; a second slurry polymerization step of performing a secondary slurry polymerization reaction of the first slurry reaction product obtained above or the first slurry reaction product and a feed composition to produce a second slurry reaction product including a prepolymer; a first gas-phase polymerization step of performing a primary gas-phase polymerization reaction of the second slurry reaction product obtained above or the second slurry reaction product obtained above and a feed composition to produce a first gas-phase reaction product including a final polymer; and a second gas-phase polymerization step of performing a secondary gas-phase polymerization reaction of the first gas-phase reaction product obtained above or the first gas-phase reaction product and a feed composition to produce a second gas-phase reaction product including a final polymer.

[0020] The slurry polymerization reaction may produce a prepolymer having a hollow structure to form the shell of the final polymer, and the gas phase polymerization reaction may fill the hollows of the prepolymer with a product having a lower density than the prepolymer to form the core of the final polymer.

[0021] Through the second slurry polymerization step, the density is 0.890 g / cm 3 ~0.940g / cm 3 and the shell portion has a density of 0.887 g / cm3 through the first gas phase polymerization step. 3 ~0.898g / cm 3 and the density of the core portion is 0.857 g / cm through the second gas phase polymerization step. 3 ~0.886g / cm 3 The core portion may be formed of the above-mentioned material.

[0022] The amount of the prepolymer produced may be 10% by weight to 60% by weight based on the total amount of the final polymer produced. In the slurry polymerization step, a molar ratio of the comonomer to the total amount of the monomer and the comonomer may be 0.01 to 0.3.

[0023] In the gas phase polymerization step, a molar ratio of the comonomer to the total amount of the monomer and the comonomer may be 0.01 to 0.2. Effect of the Invention

[0024] By using one or more slurry polymerization reactors and one or more gas phase polymerization reactors according to the present invention and controlling the operating conditions of each of the slurry polymerization reactors and the gas phase polymerization reactors, process stability can be ensured in producing a polyolefin polymer, and the polyolefin polymer produced therefrom can have a structure having a density distribution including a core portion and a shell portion, with the density of the shell portion being higher than the density of the core portion. [Brief description of the drawings]

[0025] [Figure 1a] 1 is a flowchart illustrating a method for polymerizing polyolefins according to an embodiment. [Figure 1b] 1 is a flowchart illustrating a method for polymerizing polyolefins according to an embodiment. [Figure 1c] 1 is a flowchart illustrating a method for polymerizing polyolefins according to an embodiment. [Figure 2a] 2 is a cross-sectional SEM image of the prepolymer prepared in Example 2. [Figure 2b] 1 is a cross-sectional SEM image of the final polymer produced in Example 2. [Figure 2c] 1 shows SEM images of the final polymer prepared in Example 2 before and after dissolving in xylene. [Diagram 3] 2 is a temperature rising elution fractionation (TREF) chromatogram showing the TREF value according to temperature for the final polymers prepared in Example 5 and Comparative Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The terms and words used in the description and claims of the present invention should not be interpreted limitedly to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

[0027] In the present invention, the term "stream" may mean the flow of a fluid in a process, or may mean the fluid itself flowing in a pipe. Specifically, the "stream" may mean both the fluid itself flowing in a pipe connecting each device and the flow of the fluid. In addition, the fluid may mean a gas or a liquid, and does not exclude the inclusion of a solid component in the fluid.

[0028] The present invention will be described in detail below so that those skilled in the art can easily implement the present invention, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

[0029] According to one embodiment, the polyolefin polymer comprises a core and a shell, and the core has a density of 0.857 g / cm 3 ~0.910g / cm 3 and the density of the shell portion is 0.890 g / cm 3 ~0.940g / cm 3 and the density of the shell portion may be higher than the density of the core portion.

[0030] As described above, the polyolefin polymer has a core-shell structure having a core and a shell surrounding the core, and the core and shell have the density ranges described above. The polyolefin polymer has a relatively high density in the shell, i.e., the surface of the polymer. When a low-density polymer is produced, the surface density of the polymer is low during the polymerization step, and therefore the polymer is prevented from agglomerating between polymers due to adhesion, which hinders fluidization in a gas-phase polymerization reactor, and from easily clogging peripheral devices such as piping and heat exchangers. The polymer can be produced through stable continuous operation.

[0031] In an embodiment, the polyolefin polymer may have one or more of the following physical properties (a) to (h): For example, the polyolefin polymer may have two or more or all of the following physical properties (a) to (h):

[0032] (a) Melt flow index (MIE) from 0.1g / 10min to 5.0g / 10min (2.16kg load, 190℃) (b) 0.870 g / cm 3 ~0.900g / cm 3 Density of (c) Two or more melting temperatures (T m ) (d) First melting temperature (T m1 ) and the second melting temperature (T m2 ) and the difference between the first melting temperature and the second melting temperature is 30°C to 70°C. (e) First melting temperature (T m1 ) and the second melting temperature (T m2 ) wherein the first melting temperature is 45°C to 85°C and the second melting temperature is 80°C to 125°C. (f) Two or more crystallization temperatures (T c ) (g) First crystallization temperature (T c1 ) and the second crystallization temperature (T c2 ) wherein the first crystallization temperature is 40°C to 100°C, and the second crystallization temperature is 70°C to 110°C. (h) In a temperature rising elution fractionation (TREF) chromatogram, two or more peaks are shown at temperatures of 35°C or higher, and the percentage value obtained by dividing the graph area above 60°C by the total graph area is 5% or higher.

[0033] In the above (a), the melt flow index (MIE (2.16 kg load, 190°C)) may refer to the melt flow index value of a polyolefin polymer measured according to ASTM D1238 under conditions of 190°C and a load of 2.16 kg. The melt flow index of the polyolefin polymer may be, for example, 0.1 g / 10 min to 5.0 g / 10 min, 0.5 g / 10 min to 4.0 g / 10 min, or 0.6 g / 10 min to 3.2 g / 10 min. By having a melt flow index within the above range, the process stability and processability are excellent.

[0034] In the above (b), the density may refer to the density of the polyolefin polymer measured by a density gradient tube method based on ASTM D1505. The density of the polyolefin polymer is, for example, 0.870 g / cm 3 ~0.900g / cm 3 or 0.885g / cm 3 ~0.890g / cm 3 By having a density within the above range, a polyolefin polymer having a low density can be provided.

[0035] In the above (c), the melting temperature (T m ) may mean the melting temperature of the polyolefin polymer measured based on ASTM 3417-83. The polyolefin polymer may have two or more melting temperature distributions. For example, the polyolefin polymer may have 2 to 4, 2 to 3, or 2 melting temperature distributions.

[0036] In the above (d), the polyolefin polymer has a first melting temperature (T m1 ) and the second melting temperature (T m2) and the difference between the first melting temperature and the second melting temperature may be 30°C to 70°C, 31°C to 68°C, or 33°C to 38°C.

[0037] In (e), the first melting temperature may be 45°C to 85°C, 50°C to 85°C, or 60°C to 70°C, and the second melting temperature may be 80°C to 125°C, 90°C to 120°C, or 95°C to 110°C.

[0038] In the (f), the crystallization temperature (T c ) may mean the crystallization temperature of the polyolefin polymer measured based on ASTM 3417-83, similarly to the melting temperature. The polyolefin polymer may have two or more crystallization temperature distributions. For example, the polyolefin polymer may have 2 to 4, 2 to 3, or 2 crystallization temperature distributions.

[0039] In the (g) process, the polyolefin polymer is crystallized at a first crystallization temperature (T c1 ) and the second crystallization temperature (T c2 Here, the first crystallization temperature may be 40°C to 100°C, 43°C to 97°C, or 44°C to 50°C. The second crystallization temperature may be 70°C to 110°C, 72°C to 109°C, or 74°C to 87°C.

[0040] In the above (h), the temperature rising elution fractionation (TREF) chromatogram may be obtained by analyzing the polyolefin polymer using a cross-fractionation chromatography (CFC, PolymerChar CFC-2) device. The temperature rising elution fractionation (TREF) chromatogram of the polyolefin polymer may show two or more, two to five, or two peaks at a temperature of 35°C or higher. In the temperature rising elution fractionation (TREF) chromatogram, the percentage value obtained by dividing the graph area at 60°C or higher by the total graph area may be 5% or more, 5% to 55%, or 5% to 50%. As shown above, the temperature rising elution fractionation (TREF) chromatogram shows two or more peaks, which indicates that the polyolefin polymer has a density gradient. The percentage value obtained by dividing the graph area above 60°C by the total graph area is 5% or more, which indicates that a relatively high density shell portion formed through a slurry polymerization reaction and eluted at a high temperature was well formed.

[0041] In one embodiment, the shell portion may be formed through a slurry polymerization reaction in a polyolefin polymerization system or method described below. Specifically, the shell portion having a hollow structure and a relatively high density may be formed first in the polyolefin polymer.

[0042] The density of the shell portion is, for example, 0.890 g / cm 3 ~0.940g / cm 3 , 0.895g / cm 3 ~0.930g / cm 3 or 0.900g / cm 3 ~0.922g / cm 3 may be also possible.

[0043] The melt flow index (MIE (load of 2.16 kg, 190° C.)) of the shell portion may be, 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.

[0044] The melting temperature of the shell portion may be, for example, 80°C to 125°C, 90°C to 120°C, or 95°C to 110°C. The shell portion may have one peak at a temperature of 60° C. or higher in a temperature rising elution fractionation (TREF) chromatogram.

[0045] In one embodiment, the core portion may be formed through a gas phase polymerization reaction in a polyolefin polymerization system or polymerization method described below. Specifically, the core portion in the polyolefin polymer may be formed in such a structure that the hollow of the shell portion formed through the slurry polymerization reaction is filled with a product having a relatively low density.

[0046] The density of the core portion is, for example, 0.857 g / cm 3 ~0.910g / cm 3 , 0.857g / cm 3 ~0.900g / cm 3 or 0.857 g / cm 3 ~0.898g / cm 3 may be also possible.

[0047] The melting temperature of the core portion may be, for example, 45°C to 85°C, 50°C to 85°C, or 60°C to 70°C. The weight ratio of the core part to the shell part may be 40:60 to 90:10, 50:50 to 80:20, or 50:50 to 70:30. By forming the core part and the shell part at a weight ratio within the above range, a low-density polyolefin polymer can be provided, and at the same time, the relatively low-density core part can be prevented from leaking to the surface of the polymer, thereby further improving process stability.

[0048] The polyolefin polymer formed of the core and shell portions having different physical properties as described above not only has low density characteristics, but also has a relatively high density hollow shell portion forming the surface and a relatively low density core portion filling the hollow interior of the shell portion, thereby preventing problems in which process stability is impaired due to adhesion and wettability when the density of the polymer surface is low.

[0049] The melt flow index (MIE (load of 2.16 kg, 190° C.)) of the polyolefin polymer may be, 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.

[0050] According to an embodiment, a polyolefin polymerization system includes one or more slurry polymerization reactors for slurry polymerizing a feedstream in the presence of a catalyst to produce a slurry reaction product including a prepolymer, and one or more gas-phase polymerization reactors for gas-phase polymerizing the slurry reaction product or the slurry reaction product and a feedstream to produce a gas-phase reaction product including a final polymer, the feedstream including a monomer and a comonomer, the final polymer having two or more density distributions including a core portion and a shell portion having a higher density than the core portion, and the operating temperature of the slurry polymerization reactor is 20°C to 70°C, which may be higher than the operating temperature of the gas-phase polymerization reactor.

[0051] The polyolefin polymerization system may be a system for producing a final polymer, ie, a polyolefin polymer as described above. In one embodiment, the one or more slurry polymerization reactors and the one or more gas phase polymerization reactors may be connected in series.

[0052] In one embodiment, the catalyst may be a metallocene single catalyst, which may be represented by the formula LnMQp, where M is a metal of Group IIIB, IVB, VB or VIB, Q is a hydrocarbyl group having 1 to 20 carbon atoms or a halogen, p is the valence of M minus 2, and L is a ligand bonded to the metal M.

[0053] Such metallocene catalysts are known as catalyst systems that produce polyolefins with excellent physical properties, with higher activity and copolymerization reactivity than existing Ziegler-Natta catalysts, and the metallocene catalysts can be used as homogeneous catalysts supported on a suitable support. For example, the support may be silicone and / or aluminum oxide, and specifically, silica having OH groups or other functional groups containing active hydrogen atoms, or may be in the form of porous spherical particles.

[0054] The metallocene catalyst may be supported on a support with a cocatalyst, which may be an alkylaluminoxane. The alkylaluminoxane may include linear and / or cyclic alkylaluminoxane oligomers, and when the alkylaluminoxane is a linear alkylaluminoxane oligomer, the alkylaluminoxane may have the formula R-(Al(R)-O) n In the case of a cyclic alkylaluminoxane oligomer, the chemical formula is (-Al(R)-O-) m where R is a C1-C8 alkyl group, preferably methyl, n is 1-40, preferably 10-20, and m is 3-40, preferably 3-20. The alkylaluminoxane is a mixture of oligomers having a very wide molecular weight distribution, and may usually have an average molecular weight of 800-1200.

[0055] In one embodiment, the feed stream may include a monomer and a comonomer. The monomer may be ethylene. The comonomer may be any one or more selected from the group consisting of 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, and 1-octene. As a specific example, the comonomer may be any one or more of 1-butene and 1-hexene.

[0056] The feed stream may further include a diluent. The diluent may be at least one of an inert gas and an alkane. Here, the inert gas may include nitrogen, helium, neon, etc., and the alkane may include butane, propane, isobutane, isopentane, hexane, and isomers thereof, etc. In this way, the method may include a step of contacting a catalyst with a monomer and a comonomer in a slurry polymerization reactor and a gas phase polymerization reactor using the diluent to produce a polyolefin polymer.

[0057] A polyolefin polymer, specifically a polyolefin elastomer, and more specifically a low-density polyethylene, can be produced by polymerizing a feed stream containing ethylene and a comonomer in the presence of the catalyst using a system in which one or more slurry polymerization reactors and one or more gas phase polymerization reactors are sequentially arranged.

[0058] In one embodiment, the operating temperature of the slurry polymerization reactor may be 20° C. to 70° C. or 40° C. to 60° C. Also, the operating temperature of the gas phase polymerization reactor may be lower than the operating temperature of the slurry polymerization reactor, for example, 30° C. to 50° C. or 35° C. to 48° C. By producing the final polymer as described above while reducing the operating temperature of each reactor in this manner, the portion where the sticky wetting resin interferes with the fluidization of the reactor can be minimized, and the process stability can be further improved.

[0059] In one embodiment, the operating pressure of the slurry polymerization reactor may be 5K / G to 30K / G, 10K / G to 25K / G, or 20K / G to 25K / G. The operating pressure of the gas phase polymerization reactor may be adjusted to be equal to or lower than the operating pressure of the slurry polymerization reactor, for example, the pressure of the gas phase polymerization reactor may be operated at 10K / G to 20K / G or 10K / G to 15K / G depending on the temperature of the slurry reactor. By reducing the operating pressure of each reactor and producing the final polymer as described above, the portion where the sticky wetting resin interferes with the fluidization of the reactor can be minimized, and the process stability can be further improved. Here, the pressure unit K / G is kg / cm 2 means...

[0060] In one embodiment, a prepolymer having a relatively high density and forming a shell part with a hollow structure is produced in the slurry polymerization reaction through multi-stage polymerization using one or more slurry polymerization reactors and one or more gas phase polymerization reactors, and a polyolefin polymer, i.e., polyolefin elastomer (POE), is filled into the hollow interior of the prepolymer particles in the gas phase polymerization reactor to produce a final polymer, where the final polymer may have physical properties of the polyolefin elastomer.

[0061] In one embodiment, the molar ratio of ethylene and comonomer alpha olefin in each reactor may be adjusted to 0.01-0.3 depending on the type of comonomer. For example, the molar ratio of the comonomer to the total amount of the monomer and comonomer in the slurry polymerization reactor may be 0.01-0.3, 0.05-0.3, or 0.07-0.27, and the molar ratio of the comonomer to the total amount of the monomer and comonomer in the gas phase polymerization reactor may be 0.01-0.2 or 0.05-0.18. By varying the ratio of comonomer in each reactor, it is possible to produce polymers having physical properties such as two or more melting temperatures or two or more crystallization temperatures, and the polymers having high melting temperatures and low glass transition temperatures (Tg) can exhibit great advantages in processing and physical properties.

[0062] The prepolymer produced in the slurry polymerization reactor may account for 10% by weight to 60% by weight of the total amount of the final polymer. For example, the prepolymer may be 20% by weight to 50% by weight or 30% by weight to 50% by weight of the total amount of the final polymer. By controlling the weight ratio of the prepolymer to the total amount of the final polymer within the above range, the overall density is increased, a relatively high density shell is firmly formed without impairing the physical properties of the final polymer, and the polymer produced in the gas phase polymerization reactor is hardly present outside, thereby improving process stability.

[0063] In one embodiment, the gas phase polymerization reactor has an MIT 15 The temperature below MIT15 is for the purpose of operating each reactor at a low temperature and setting the process operating temperature in order to ensure process stability. 15 The temperature below is measured using a DSC instrument according to the ASTM 3417-83 method, and is measured based on the part where a 15 wt% melt area percent appears in the first scan from 25°C to 200°C under the condition of 10°C / min.

[0064] For example, the gas phase polymerization reactor 15 The temperature below may be 40°C to 80°C, 40°C to 70°C, or 40°C to 65°C. 15 If the gas phase polymerization reactor is controlled at the same temperature as the temperature of the reactor, the polymer will aggregate, which may reduce the process stability. In addition, if the reactor temperature is operated at a very low temperature in order to ensure process stability, there is a drawback in that the production volume will be very low. In addition, in the process of producing a polyolefin polymer having a high comonomer content, a situation where the proportion of comonomer is locally high occurs when the production volume increases, which increases the viscosity of the polymer and produces heteropolymers, which may cause process troubles. 15By controlling the temperature of the gas phase polymerization reactor, such problems can be prevented.

[0065] In one embodiment, when the slurry polymerization reactor is disposed in front of the gas phase polymerization reactor, it is possible to prevent the metallocene catalyst from being directly exposed to the conditions of the gas phase polymerization reactor, and also to increase the size of the polymer through the slurry polymerization reaction, which is helpful for process stability. Also, when a low density prepolymer is produced in a slurry polymerization reactor, the amount of polymer having the physical properties of polyolefin elastomer increases on the outside, which may cause the polymer to have stickiness overall, which may hinder process stability.

[0066] According to an embodiment, the final polymer may be the polyolefin polymer described above. Specifically, the final polymer may include a core portion and a shell portion, and the density of the core portion may be 0.857 g / cm 3 ~0.910g / cm 3 and the density of the shell portion is 0.890 g / cm 3 ~0.940g / cm 3 and the density of the shell portion may be higher than the density of the core portion.

[0067] The final polymer may have one or more of the following physical properties (a) to (h): For example, the polyolefin polymer may have two or more or all of the following physical properties (a) to (h):

[0068] (a) Melt flow index (MIE) from 0.1g / 10min to 5.0g / 10min (2.16kg load, 190℃) (b) 0.870 g / cm 3 ~0.900g / cm 3 Density of (c) Two or more melting temperatures (T m ) (d) First melting temperature (T m1 ) and the second melting temperature (T m2 ) and the difference between the first melting temperature and the second melting temperature is 30°C to 70°C. (e) First melting temperature (T m1 ) and the second melting temperature (T m2 ) wherein the first melting temperature is 45°C to 85°C and the second melting temperature is 80°C to 125°C. (f) Two or more crystallization temperatures (T c ) (g) First crystallization temperature (T c1 ) and the second crystallization temperature (T c2 ) wherein the first crystallization temperature is 40°C to 100°C, and the second crystallization temperature is 70°C to 110°C. (h) In a temperature rising elution fractionation (TREF) chromatogram, two or more peaks are shown at temperatures of 35°C or higher, and the percentage value obtained by dividing the graph area above 60°C by the total graph area is 5% or higher.

[0069] In one embodiment, the shell, i.e., the prepolymer produced in a slurry polymerization reactor, has a density of, for example, 0.890 g / cm 3 ~0.940g / cm 3 , 0.895g / cm 3 ~0.930g / cm 3 or 0.900g / cm 3 ~0.922g / cm 3 may be also possible.

[0070] The melt flow index (MIE (load of 2.16 kg, 190° C.)) of the shell portion may be, 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.

[0071] The melting temperature of the shell portion may be, for example, 80°C to 125°C, 90°C to 120°C, or 95°C to 110°C. The shell portion may have one peak at a temperature of 60° C. or higher in a temperature rising elution fractionation (TREF) chromatogram.

[0072] In one embodiment, the density of the core portion formed in the hollow interior of the prepolymer through the gas phase polymerization reaction is, for example, 0.857 g / cm 3 ~0.910g / cm 3 , 0.857g / cm 3 ~0.900g / cm 3 or 0.857 g / cm 3 ~0.898g / cm 3 may be also possible.

[0073] The melting temperature of the core portion may be, for example, 45°C to 85°C, 50°C to 85°C, or 60°C to 70°C. The melt flow index (MIE (2.16 kg load, 190° C.)) of the final polymer may be, 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.

[0074] In the final polymer, the weight ratio of the core part to the shell part may be 40:60 to 90:10, 50:50 to 80:20, or 50:50 to 70:30. By forming the core part and the shell part at a weight ratio within the above range, it is possible to provide a final polymer that has the characteristics of a polyolefin elastomer such as low density and can prevent the process stability from being impaired due to the tackiness and wettability.

[0075] As described above, the shell and core have different physical properties, and one polyolefin polymer exhibits two or more characteristics such as melting temperature and crystallization temperature. As an example, the polyolefin polymerization system may include one slurry polymerization reactor and one gas-phase polymerization reactor. In this case, the polyolefin polymerization system may include a first slurry polymerization reactor that performs a slurry polymerization reaction of a feed stream supplied in the presence of a catalyst to produce a slurry reaction product including a prepolymer, and a second gas-phase polymerization reactor that receives the slurry reaction product or the slurry reaction product and a feed stream and performs a gas-phase polymerization reaction to produce a gas-phase reaction product including a final polymer.

[0076] As another example, the polyolefin polymerization system may include one slurry polymerization reactor and two gas-phase polymerization reactors. In this case, the polyolefin polymerization system may include a first slurry polymerization reactor that performs a slurry polymerization reaction of a feed stream supplied in the presence of a catalyst to produce a slurry reaction product containing a prepolymer, a first gas-phase polymerization reactor that receives the slurry reaction product from the first slurry polymerization reactor or the slurry reaction product and a feed stream and performs a gas-phase polymerization reaction to produce a first gas-phase reaction product containing a final polymer, and a second gas-phase polymerization reactor that receives the first gas-phase reaction product from the first gas-phase polymerization reactor or the first gas-phase reaction product and a feed stream and performs a gas-phase polymerization reaction to produce a second gas-phase reaction product containing a final polymer.

[0077] As yet another example, the polyolefin polymerization system may include two slurry polymerization reactors and two gas-phase polymerization reactors. In this case, the polyolefin polymerization system may include a first slurry polymerization reactor that performs a slurry polymerization reaction of a feed stream supplied in the presence of a catalyst to produce a first slurry reaction product containing a prepolymer, a second slurry polymerization reactor that receives the first slurry reaction product or the first slurry reaction product and a feed stream from the first slurry polymerization reactor and performs a slurry polymerization reaction to produce a second slurry reaction product containing a prepolymer, a first gas-phase polymerization reactor that receives the second slurry reaction product or the second slurry reaction product and a feed stream from the second slurry polymerization reactor and performs a gas-phase polymerization reaction to produce a first gas-phase reaction product containing a final polymer, and a second gas-phase polymerization reactor that receives the first gas-phase reaction product or the first gas-phase reaction product and a feed stream from the first gas-phase polymerization reactor and performs a gas-phase polymerization reaction to produce a second gas-phase reaction product containing a final polymer.

[0078] In one embodiment, the first gas phase reaction product produced in the first gas phase polymerization reactor is separated into unreacted gas and polymer using a filter, and the separated polymer is supplied to the second gas phase polymerization reactor, and the unreacted gas is returned to the first slurry polymerization reactor and / or the second slurry polymerization reactor via a purification tower.

[0079] If the temperature of the gas phase polymerization reactor is operated at a very low temperature, the production volume is disadvantageously very low. In addition, in the process of producing a polyolefin polymer having a high comonomer content, when the production volume increases, a situation where the comonomer ratio is locally high occurs, which increases the viscosity of the polymer and produces heteropolymers, which can cause process troubles. In the present invention, however, a method of reducing the viscosity of the polymer under high comonomer concentration conditions using a high sorption mode is applied.

[0080] As a specific example, the first gas phase polymerization reactor may not be operated in high sorption mode, and the second gas phase polymerization reactor may be operated in high sorption mode. The second gas phase polymerization reactor may be operated under temperature and pressure conditions at which the gas injected is condensed and the gas discharged from the reactor is not condensed.

[0081] For reference, the polyolefin polymerization system may include a circulation line extending from an upper portion of the gas phase polymerization reactor and connected to a lower portion of the gas phase polymerization reactor for circulating a circulation gas stream, a compressor provided in the circulation line, and a heat exchanger provided in the circulation line downstream of the compressor based on the flow direction of the circulation gas stream. In the high sorption mode, the sorbent may be used in an amount of 0.1 to 30 parts by weight, 2 to 20 parts by weight, or 3 to 15 parts by weight per 100 parts by weight of the total circulation gas stream.

[0082] Sorbents used when the second gas phase polymerization reactor is operated in high sorption mode may include propane, isobutane, isopentane, hexane, and the like. According to an embodiment, a method for polymerizing polyolefin includes a slurry polymerization step of slurry-polymerizing a feed composition including a monomer and a comonomer in the presence of a catalyst at least once to produce a slurry reaction product including a prepolymer, and a gas-phase polymerization step of gas-phase polymerizing the slurry reaction product obtained in the above step or the slurry reaction product and a feed composition at least once to produce a gas-phase reaction product including a final polymer, the reaction temperature of the slurry polymerization step being 20°C to 70°C, which is higher than the reaction temperature of the gas-phase polymerization step, and the final polymer may have two or more density distributions including a core portion and a shell portion having a higher density than the core portion.

[0083] The polyolefin polymerization method may be a method for producing a final polymer, i.e., the polyolefin polymer, using the polyolefin polymerization system described above. In one embodiment, the catalyst may be a metallocene single catalyst, which may be represented by the formula LnMQp, where M is a metal of Group IIIB, IVB, VB or VIB, Q is a hydrocarbyl group having 1 to 20 carbon atoms or a halogen, p is the valence of M minus 2, and L is a ligand bonded to the metal M.

[0084] Such metallocene catalysts are known as catalyst systems that produce polyolefins with excellent physical properties, with higher activity and copolymerization reactivity than existing Ziegler-Natta catalysts, and the metallocene catalysts can be used as homogeneous catalysts supported on a suitable support. For example, the support may be silicone and / or aluminum oxide, and as a specific example, it may be silica having OH groups or other functional groups containing active hydrogen atoms, or may be in the form of porous spherical particles.

[0085] The metallocene catalyst may be supported on a support with a cocatalyst, which may be an alkylaluminoxane. The alkylaluminoxane may include linear and / or cyclic alkylaluminoxane oligomers, and when the alkylaluminoxane is a linear alkylaluminoxane oligomer, the alkylaluminoxane may have the formula R-(Al(R)-O) n In the case of a cyclic alkylaluminoxane oligomer, the chemical formula is (-Al(R)-O-) m where R is a C1-C8 alkyl group, preferably methyl, n is 1-40, preferably 10-20, and m is 3-40, preferably 3-20. The alkylaluminoxane is a mixture of oligomers having a very wide molecular weight distribution, and may usually have an average molecular weight of 800-1200.

[0086] In one embodiment, the feed stream may include a monomer and a comonomer. The monomer may be ethylene. The comonomer may be at least one selected from the group consisting of 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, and 1-octene. As a specific example, the comonomer may be at least one of 1-butene and 1-hexene.

[0087] The feed stream may further include a diluent. The diluent may be at least one of an inert gas and an alkane. Here, the inert gas may include nitrogen, helium, neon, etc., and the alkane may include butane, propane, isobutane, isopentane, hexane, and isomers thereof, etc. In this way, the method may include a step of contacting the monomer and comonomer with the diluent in a slurry polymerization reactor and a gas phase polymerization reactor to produce a polyolefin polymer.

[0088] A polyolefin polymer, specifically a polyolefin elastomer, and more specifically a low-density polyethylene, can be produced by polymerizing a feed stream containing ethylene and a comonomer in the presence of the catalyst using a system in which one or more slurry polymerization reactors and one or more gas phase polymerization reactors are sequentially arranged.

[0089] In an embodiment, the temperature of the slurry polymerization reaction may be 20° C. to 70° C. or 40° C. to 60° C. Also, the temperature of the gas phase polymerization reaction may be lower than the temperature of the slurry polymerization reaction, for example, 30° C. to 50° C. or 35° C. to 48° C. By producing the final polymer as described above by reducing the operating temperature of each reaction in this manner, the portion where the sticky wetting resin interferes with the fluidization of the reactor can be minimized, and the process stability can be further improved.

[0090] In one embodiment, the pressure of the slurry polymerization reaction may be 5K / G to 30K / G, 10K / G to 25K / G, or 20K / G to 25K / G. The pressure of the gas phase polymerization reaction may be adjusted to a temperature lower than the operating pressure of the slurry polymerization reaction, for example, 10K / G to 20K / G or 10K / G to 15K / G depending on the temperature. By producing the final polymer as described above by reducing the pressure of each reactor in this manner, the portion where the sticky wetting resin interferes with the fluidization of the reactor can be minimized, and the process stability can be further improved.

[0091] In one embodiment, a multi-stage polymerization process is carried out by performing one or more slurry polymerization reactions and one or more gas phase polymerization reactions. In the slurry polymerization reaction, a prepolymer having a relatively high density and forming a shell part with a hollow structure is produced, and in the gas phase polymerization reaction, a polyolefin polymer, i.e., a polyolefin elastomer (POE), is filled into the hollow interior of the prepolymer particles to produce a final polymer, where the final polymer may have the physical properties of a polyolefin elastomer.

[0092] In one embodiment, the molar ratio of ethylene and comonomer alpha olefin in each reaction can be adjusted to 0.01-0.3 depending on the type of comonomer. For example, the molar ratio of the comonomer to the total amount of the monomer and comonomer in the slurry polymerization reaction can be 0.01-0.3, 0.05-0.3, or 0.07-0.27, and the molar ratio of the comonomer to the total amount of the monomer and comonomer in the gas phase polymerization reaction can be 0.01-0.2 or 0.05-0.18. By varying the ratio of comonomer in each reaction, it is possible to produce polymers having physical properties such as two or more melting temperatures or two or more crystallization temperatures, and the polymers having high melting temperatures and low glass transition temperatures (Tg) can exhibit great advantages in processing and physical properties.

[0093] The prepolymer produced by the slurry polymerization reaction may account for 10% to 60% by weight of the total amount of the final polymer. For example, the prepolymer may be 20% to 50% by weight or 30% to 50% by weight of the total amount of the final polymer. By controlling the weight ratio of the prepolymer to the total amount of the final polymer within the above range, the overall density is increased, a relatively high density shell is firmly formed without impairing the physical properties of the final polymer, and the polymer produced in the gas phase polymerization reactor is hardly present outside, thereby improving process stability.

[0094] In one embodiment, the gas phase polymerization reaction is carried out at a temperature of 100° C. or lower, preferably 100° C. or lower, and more preferably 150° C. or lower, more preferably 100° C. or lower. 15 (15 wt % melting initiation temperature). 15 The temperature below 100° C. is for controlling the temperature of each reaction low and setting an appropriate temperature range to ensure process stability. 15 The temperature below is measured using a DSC instrument according to the ASTM 3417-83 method, and is measured based on the part where a 15 wt% melt area percent appears in the first scan from 25°C to 200°C under the condition of 10°C / min.

[0095] For example, in the gas phase polymerization reaction, MIT 15 The temperature below may be 40°C to 80°C, 40°C to 70°C, or 40°C to 65°C. 15If the gas phase polymerization reaction is controlled at the same temperature as the temperature, the polymer may aggregate, which may reduce the process stability. In addition, if the reactor temperature is operated at a very low temperature to ensure process stability, there is a drawback in that the production volume is very low. In addition, in the process of producing a polyolefin polymer having a high comonomer content, a situation where the proportion of comonomer is locally high occurs when the production volume increases, which may increase the viscosity of the polymer and produce heteropolymers, which may cause process troubles. However, by controlling the temperature of the gas phase polymerization reaction at a temperature of less than MIT15 within the above range, such problems can be prevented.

[0096] In one embodiment, when the slurry polymerization is arranged in the front stage of the gas phase polymerization reactor, not only can the metallocene catalyst be prevented from being directly exposed to the conditions of the gas phase polymerization, but the size of the polymer can be further increased through the slurry polymerization, which is helpful for process stability. Meanwhile, when a low density prepolymer is produced by the slurry polymerization, the amount of polymer having the physical properties of polyolefin elastomer increases on the outside, and the polymer becomes sticky overall, which may cause a problem of impairing process stability.

[0097] In one embodiment, the slurry polymerization reaction may produce a prepolymer having a hollow structure to form the shell of the final polymer, and the gas phase polymerization reaction may fill the hollow of the prepolymer with a product having a lower density than the prepolymer to form the core of the final polymer.

[0098] Here, the final polymer may be the polyolefin polymer described above. Specifically, the density of the final polymer is 0.890 g / cm3 or less through the slurry polymerization step. 3 ~0.940g / cm 3 and the density of the shell portion is 0.857 g / cm through the gas phase polymerization step. 3 ~0.910g / cm 3 The core portion can be formed as follows.

[0099] The final polymer may have one or more of the following physical properties (a) to (h): For example, the polyolefin polymer may have two or more or all of the following physical properties (a) to (h):

[0100] (a) Melt flow index (MIE) from 0.1g / 10min to 5.0g / 10min (2.16kg load, 190℃) (b) 0.870 g / cm 3 ~0.900g / cm 3 Density of (c) Two or more melting temperatures (T m ) (d) First melting temperature (T m1 ) and the second melting temperature (T m2 ) and the difference between the first melting temperature and the second melting temperature is 30°C to 70°C. (e) First melting temperature (T m1 ) and the second melting temperature (T m2 ), the first melting temperature is 45°C to 85°C, and the second melting temperature is 80°C to 125°C. (f) Two or more crystallization temperatures (T c ) (g) First crystallization temperature (T c1 ) and the second crystallization temperature (T c2 ) wherein the first crystallization temperature is 40°C to 100°C, and the second crystallization temperature is 70°C to 110°C. (h) In a temperature rising elution fractionation (TREF) chromatogram, two or more peaks are shown at temperatures of 35°C or higher, and the percentage value obtained by dividing the graph area above 60°C by the total graph area is 5% or higher.

[0101] In one embodiment, the shell, i.e., the prepolymer produced in a slurry polymerization reactor, has a density of, for example, 0.890 g / cm 3 ~0.940g / cm 3 , 0.895g / cm 3 ~0.930g / cm 3 or 0.900g / cm 3 ~0.922g / cm 3 may be also possible.

[0102] The melt flow index (MIE (load of 2.16 kg, 190° C.)) of the shell portion may be, 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.

[0103] The melting temperature of the shell portion may be, for example, 80°C to 125°C, 90°C to 120°C, or 95°C to 110°C. The shell portion may have one peak at a temperature of 60° C. or higher in a temperature rising elution fractionation (TREF) chromatogram.

[0104] In one embodiment, the density of the core portion formed in the hollow interior of the prepolymer through the gas phase polymerization reaction is, for example, 0.857 g / cm 3 ~0.910g / cm 3 , 0.855g / cm 3 ~0.900g / cm 3 or 0.857 g / cm 3 ~0.898g / cm 3 may be also possible.

[0105] The melting temperature of the core portion may be, for example, 45°C to 85°C, 50°C to 85°C, or 60°C to 70°C. The melt flow index (MIE (2.16 kg load, 190° C.)) of the final polymer may be, 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. In the final polymer, the weight ratio of the core part to the shell part may be 40:60 to 90:10, 50:50 to 80:20, or 50:50 to 70:30. By forming the core part and the shell part at a weight ratio within the above range, it is possible to provide a final polymer that has the properties of a polyolefin elastomer as a low density and is capable of preventing the process stability from being impaired due to the stickiness or wettability.

[0106] As described above, the shell and core have different physical properties, and one polyolefin polymer exhibits two or more characteristics such as melting temperature and crystallization temperature. For example, the polyolefin polymerization method may include a slurry polymerization step of slurry polymerizing a feed composition including a monomer and a comonomer in the presence of the catalyst to produce a slurry reaction product including a prepolymer, and a gas-phase polymerization step of gas-phase polymerizing the slurry reaction product obtained in the above step or the slurry reaction product and a feed composition to produce a final polymer.

[0107] 1A is a flow chart showing a method for polymerizing polyolefins according to an embodiment. Specifically, as shown in FIG. 1A, the polyolefin polymerization method includes a slurry polymerization reaction (100) and a gas phase polymerization reaction (200) performed sequentially.

[0108] As another example, the polyolefin polymerization method may include a first slurry polymerization step of slurry polymerizing a feed composition including a monomer and a comonomer in the presence of a catalyst to produce a slurry reaction product including a prepolymer; a first gas-phase polymerization step of primary gas-phase polymerization of the slurry reaction product obtained above, or the slurry reaction product obtained above and a feed composition to produce a first gas-phase reaction product including a final polymer; and a second gas-phase polymerization step of secondary gas-phase polymerization of the first gas-phase reaction product obtained above, or the first gas-phase reaction product obtained above and a feed composition to produce a second gas-phase reaction product including a final polymer.

[0109] As yet another example, the polyolefin polymerization method may include a first slurry polymerization step of performing a primary slurry polymerization reaction of a feed composition including a monomer and a comonomer in the presence of a catalyst to produce a first slurry reaction product including a prepolymer; a second slurry polymerization step of performing a secondary slurry polymerization reaction of the first slurry reaction product obtained above or the first slurry reaction product and a feed composition to produce a second slurry reaction product including a prepolymer; a first gas-phase polymerization step of performing a primary gas-phase polymerization reaction of the second slurry reaction product obtained above or the second slurry reaction product obtained above and a feed composition to produce a first gas-phase reaction product including a final polymer; and a second gas-phase polymerization step of performing a secondary gas-phase polymerization reaction of the first gas-phase reaction product obtained above or the first gas-phase reaction product and a feed composition to produce a second gas-phase reaction product including a final polymer.

[0110] 1B is a flow chart showing a method for polymerizing a polyolefin according to an embodiment. Specifically, as shown in FIG. 1B, the polyolefin polymerization method includes a first slurry polymerization reaction (110), a second slurry polymerization reaction (120), a first gas phase polymerization reaction (210), and a second gas phase polymerization reaction (220) sequentially performed.

[0111] In one embodiment, the first gas phase reaction product produced in the first gas phase polymerization reaction is filtered through a filter to separate unreacted gas and polymer, and the separated polymer is used to carry out a second gas phase polymerization reaction, and the unreacted gas can be reused in the first slurry polymerization reaction and / or the second slurry polymerization reaction.

[0112] Fig. 1c is a flow chart showing a method for polymerizing polyolefin according to an embodiment. Specifically, as shown in Fig. 1c, the polyolefin polymerization method sequentially performs a first slurry polymerization reaction (110), a second slurry polymerization reaction (120), a first gas phase polymerization reaction (210) and a second gas phase polymerization reaction (220), and the first gas phase reaction product generated in the first gas phase polymerization reaction (210) is filtered through a filter to separate unreacted gas and polymer, and the separated polymer is used to perform a second gas phase polymerization reaction (220), and the unreacted gas can be reused in the first slurry polymerization reaction (110) and / or the second slurry polymerization reaction (120).

[0113] If the temperature of the gas phase polymerization reaction is very low, the production volume is very low. In addition, in the process of producing a polyolefin polymer having a high comonomer content, when the production volume increases, the comonomer ratio is locally high, which increases the viscosity of the polymer and produces heteropolymers, which can cause process troubles. In the present invention, however, a method of reducing the viscosity of the polymer under high comonomer concentration conditions using a high sorption mode is applied.

[0114] As a specific example, the first gas phase polymerization reactor may not be operated in high sorption mode, and the second gas phase polymerization reactor may be operated in high sorption mode. The second gas phase polymerization reactor may be operated under temperature and pressure conditions at which the gas injected is condensed and the gas discharged from the reactor is not condensed.

[0115] For reference, the gas phase polymerization reaction can be carried out using a circulation line that extends from the upper part of a gas phase polymerization reactor and is connected to the lower part of the gas phase polymerization reactor, for circulating a circulation gas stream, a compressor provided in the circulation line, and a heat exchanger provided in the circulation line downstream of the compressor based on the flow direction of the circulation gas stream. In the high sorption mode, the sorbent can be used in an amount of 0.1 to 30 parts by weight, 2 to 20 parts by weight, or 3 to 15 parts by weight per 100 parts by weight of the total circulation gas stream.

[0116] Sorbents for use when the second gas phase polymerization reaction is operated in a high sorption mode may include propane, isobutane, isopentane, hexane, and the like. When the polyolefin is polymerized through two slurry polymerization steps and two gas phase polymerization steps, the density is 0.890 g / cm3 through the two slurry polymerization steps. 3 ~0.940g / cm 3 and the shell portion has a density of 0.887 g / cm3 through the first gas phase polymerization step. 3 ~0.898g / cm 3 and the density of the core portion is 0.857 g / cm through the second gas phase polymerization step. 3 ~0.886g / cm 3 The core portion can be formed as follows.

[0117] Through the two slurry polymerization steps, the density is, for example, 0.890 g / cm 3 ~0.940g / cm 3 , 0.895g / cm 3 ~0.930g / cm 3 or 0.900g / cm 3 ~0.922g / cm 3 The shell portion can be formed as follows.

[0118] Through the first gas phase polymerization step, the density was 0.887 g / cm 3 ~0.898g / cm 3 or 0.888g / cm 3 ~0.897g / cm 3 The core portion can be formed as follows. Through the second gas phase polymerization step, the density was 0.857 g / cm 3 ~0.886g / cm 3 or 0.857 g / cm 3 ~0.884g / cm 3 The core portion can be formed as follows.

[0119] In this way, a polyolefin polymer can be produced by forming a shell part with a relatively high density through the slurry polymerization reaction, forming a core part with a lower density than that of the slurry polymerization reaction through the first gas phase polymerization reaction, and forming a core part with an even lower density than that of the first gas phase polymerization reaction through the second gas phase polymerization reaction. This difference in density gradient can improve process stability when the catalyst prepares a prepolymer with a relatively high density in the slurry polymerization reaction compared to the gas phase polymerization reaction and proceeds to the first and second gas phase polymerization reactions in the future. The produced polyolefin polymer can have a high melting temperature and a low melting temperature, i.e., two or more melting temperatures, and a low glass transition temperature due to the density gradient. Due to the characteristics of this polyolefin polymer, the turnover rate increases during molding, increasing processing productivity, and the physical properties such as rebound resilience can be improved due to the low glass transition temperature.

[0120] Specific examples of the present invention will be presented below. However, the examples described below are merely for the purpose of specifically illustrating and explaining the present invention, and are not intended to limit the present invention. In addition, since the contents not described here can be sufficiently inferred by those skilled in the art, the description thereof will be omitted.

[0121] (Production of polyolefin polymers) [Examples 1 to 4 and Comparative Examples 1 to 2] A polyolefin polymer, specifically, a linear low-density polyethylene, was produced using one slurry polymerization reactor and one gas phase polymerization reactor under the operating conditions shown in Table 1 below.

[0122] The catalyst composition prepared by combining a metallocene catalyst, methylaluminoxane (MAO) and a porous support was used to carry out polymerization reactions in a batch polymerization reactor under simulating slurry and gas phase polymerization conditions.

[0123] In order to control the polymerization temperature, a 2 L jacketed stainless steel autoclave reactor capable of supplying external cooling water was heated from room temperature to 110° C., and then purged with nitrogen and 400 ml of isobutane.

[0124] After temperature adjustment, 1.5 ml of 0.2 M triethylaluminum (TEAL), 2.5 ml (1.1 mmol in hexane) of an antistatic agent (Statsafe 6000, Innospec) and 1 L of isobutane were added to the reactor.

[0125] Next, ethylene, 1-hexene (wt%, 1-hexene input relative to ethylene input), and hydrogen (mg / kgC2, hydrogen input (mg) relative to 1 kg of ethylene input) were charged, and the supported catalyst was charged into the reactor. A slurry polymerization reaction was carried out under the polymerization conditions shown in Table 1 below. During the polymerization, the ethylene partial pressure was maintained constant, and 1-hexene and hydrogen were continuously charged in conjunction with ethylene. After the slurry polymerization was completed, unreacted 1-hexene and isobutane were discharged.

[0126] For the gas phase polymerization reaction, the gas phase polymerization reactor was injected with nitrogen as a diluent at 100 psi, and the temperature was adjusted to 48° C. while injecting 250 ppm of an antistatic agent. After adjusting the temperature, gas phase polymerization reaction was carried out according to the polymerization conditions shown in Table 1 below. After the reaction was completed, the unreacted gas was discharged and the reactor was opened to obtain a linear low density polyethylene (LLDPE) resin having free flowability as the final polymer, and its physical properties were measured and shown.

[0127] [Table 1] TIFF2025042592000003.tif120170

[0128] The methods for measuring the properties in Table 1 and Table 2 below are as follows. Melt Flow Index (MIE, MI2.16): Measured according to ASTM D1238 at 190°C and a load of 2.16 kg.

[0129] High Load Melt Flow Index (MIF, MI21.6): Measured according to ASTM D1238 at 190°C and a load of 21.6 kg. Melt flow index ratio (SR, MFRR): Calculated as MIF / MIE (F / E).

[0130] Density: Measured by density gradient tube method according to ASTM D1505. BD: Bulk density, measured according to ASTM D1895. Molecular weight and molecular weight distribution: Measurements were performed using a gel permeation chromatography (GPC-RI, Polymer Laboratory Inc. 220 System) with a refractive index detector (RI Detector) as follows. Two Olexis and one Guard were used as separation columns, and the column temperature was maintained at 160°C. Calibration was performed using a standard polystyrene set from Polymer Laboratory Inc. The eluent was trichlorobenzene containing 0.0125 wt% antioxidant (BHT), and the sample concentration was 1.0 mg / ml. The measurement was performed for 27 minutes under the conditions of an injection volume of 0.2 ml and a pump flow rate of 1.0 ml / min. The number average molecular weight (Mn), weight average molecular weight (Mw), and Z average molecular weight (Mz) were calculated by converting them to polyethylene after universal calibration using polystyrene standard substances Easical A and Easical B (Agilent products).

[0131] Melting temperature (T m ), crystallization temperature (T c ): Measured using a DSC instrument according to ASTM 3417-83 method, and the values ​​obtained in the second scan in the temperature range of 25 to 200°C at 10°C / min were used.

[0132] Glass transition temperature (Tg ): Measured using a DSC instrument according to ASTM 3417-83 method, and the values ​​obtained in the second scan in the temperature range of -80 to 200°C at a rate of 40°C / min were used. MIT 15 : Measured using a DSC device according to the ASTM 3417-83 method, and the part where a melt area percent of 15 wt% appears in the first scan from 25 to 200°C at a rate of 10°C / min was used as the standard.

[0133] Comonomer (wt%): Analyzed and calculated via 13C NMR according to ASTM D5017. Temperature rising elution fractionation (TREF): Analysis was performed using a cross-fractionation chromatography (CFC; PolymerChar CFC-2) apparatus as follows. Two Olexis and one Guard were used as separation columns, the column temperature was maintained at 150°C, and calibration was performed using a standard polystyrene set from Polymer Laboratory Inc. Trichlorobenzene containing 0.0125 wt% antioxidant (BHT) was used as the eluent, the sample concentration was 75 mg / mL, and the pump flow rate was 1.0 mL / min. After sample injection, the oven and sample temperatures were raised to 150°C at a heating rate of 40°C / min, and the temperature was maintained at 150°C for 60 minutes, and then the temperature of the sample was reduced to 95°C at a cooling rate of 40°C / min. After maintaining at 95°C for 45 minutes, the temperature was further cooled to 30°C at a cooling rate of 0.5°C / min and maintained for 30 minutes. Then, the temperature of the sample was raised from 35°C to 120°C, and the temperature was divided into 22 fractions at 4°C intervals. 0.5 mL of sample was injected into each fraction, and the eluted fraction passed through the TREF column and the Olexis column, obtaining the TREF value and molecular weight simultaneously. The molecular weight was calculated by converting it to polyethylene after universal calibration using polystyrene standard substances Easical A and Easical B (Agilent products). Data processing was performed using the analysis program "CFC Calibration" attached to the instrument, and the analysis took about 600 minutes. An infrared spectrometer was used as a detector.

[0134] Single density: Calculated using the following formula 1.

[0135]

number

[0136] In the above formula 1, d is the density of the final polymer, d1 and m1 are the individual density and fraction (wt%) of the polymer produced in the first slurry polymerization reactor, d2 and m2 are the individual density and fraction (wt%) of the polymer produced in the second slurry polymerization reactor, d3 and m3 are the individual density and fraction (wt%) of the polymer produced in the first gas phase polymerization reactor, d4 and m4 are the individual density and fraction (wt%) of the polymer produced in the second gas phase polymerization reactor, and m1 + m2 + m3 + m4 = 1.

[0137] Here, in the case of Examples 1 to 4 and Comparative Examples 1 and 2 in which one slurry polymerization reactor and one gas-phase polymerization reactor were used, it was assumed that a first slurry polymerization reactor and a second gas-phase polymerization reactor were used, and factors related to the second slurry polymerization reactor and the first gas-phase polymerization reactor were excluded from the formulas for calculation.

[0138] [Examples 5 to 7 and Comparative Example 3] A catalyst composition (M-Cat') prepared by combining a metallocene catalyst, methylaluminoxane (MAO) and a porous support was used to produce polyolefin polymer, specifically linear low density polyethylene, using two slurry polymerization reactors and two gas phase polymerization reactors. The operating conditions of each reactor are shown in Table 2 below.

[0139] The fluidized beds of the first and second slurry polymerization reactors are composed of polymer particle granules. 1-Butene, ethylene, and hydrogen are mixed together in a pipe and injected into a circulation line. The composition injected and the physical properties of the generated prepolymer are shown in Table 2 below.

[0140] The injection concentrations of ethylene, hydrogen and 1-butene in the first and second gas phase polymerization reactors were adjusted to maintain the compositions shown in Table 2. The prepolymer was fed to account for 5% to 10% by weight of the total weight of the present polymerization composition (prepolymer + ethylene + 1-butene), and the remaining molar percentages other than ethylene, hydrogen and 1-butene in the component concentrations of the first and second gas phase polymerization reactors in Table 2 below are propane as a diluent.

[0141] The concentrations of all gases were measured by online gas chromatography of the gas in the circulating gas stream. The reaction product discharged from the first gas-phase polymerization reactor passed through a filter to separate the unreacted gas from the polymer, after which the polymer was transferred to the second gas polymerization reactor, and the separated unreacted gas was injected into the first slurry polymerization reactor through a purification tower. 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 operated so that the height of the fluidized bed of the gas-phase polymerization reactor was maintained constant. To maintain a constant operating temperature, the heat generated in the polymerization reaction was removed by adjusting the temperature of the circulating gas using a heat exchanger.

[0142] Thereafter, the reaction product was discharged from the second gas phase polymerization reactor, and the reaction product was subjected to processes such as degassing and drying to obtain a linear low density polyethylene (LLDPE) resin as the final polymer. The physical properties of the LLDPE resin were measured and are shown in Table 2.

[0143] [Table 2] TIFF2025042592000006.tif177170

[0144] In Table 2, the comonomer means 1-butene, and the molar ratio of the comonomer means the molar ratio of 1-butene to the total amount of ethylene and 1-butene. (Experimental Example) Experimental Example 1: Confirmation of polyolefin polymer structure [1. Cross section of prepolymer] 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 microscopy (SEM), and the photographed image is shown in FIG. 2a.

[0145] Referring to FIG. 2a, it can be seen that a prepolymer having a hollow structure was produced through the slurry polymerization reaction, and the shell portion of the final polymer was formed. [2. Cross section of the final polymer] 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 microscopy (SEM), and the photographed image is shown in Figure 2b. Here, the densities of the shell and core parts are shown on the image.

[0146] Referring to FIG. 2b, it was confirmed that a relatively low density core was formed in the hollow of the prepolymer through the gas phase polymerization reaction. [3. Cross-section of the final polymer before and after dissolving in xylene] A scanning electron microscope (SEM) was used to photograph 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 dissolving in a xylene solution, and the photographed images are shown in Figure 2c. Specifically, the left image in Figure 2c 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.

[0147] The xylene dissolution experiment is an experiment that can confirm that a part with low density and high MI dissolves in xylene and dissolves, and as shown in Figure 2c, when the final polymer is dissolved in xylene, it can be confirmed that only the core part with a relatively low density dissolves, and the shell part with a high density of 0.916 level remains undissolved. Through this, it can be confirmed that the final polymer according to the present invention has a core-shell structure in which a core part with a low density is formed on the inside and a shell part with a high density is formed on the outside surrounding the core part.

[0148] Experimental Example 2: Confirmation of TREF of polyolefin polymer For the final polymers prepared in Examples 1 to 7 and Comparative Example 3, the TREF values ​​according to temperature were measured by the above-mentioned method, and the TREF chromatograms were derived, which can be seen in Tables 1 and 2. The TREF chromatograms derived for the final polymers prepared in Example 5 and Comparative Example 3 can also be seen in FIG. 3.

[0149] 3, it can be seen that the final polymers according to Examples 1 to 7 show two peaks at temperatures of 35° C. or higher, and the percentage value obtained by dividing the graph area at temperatures of 60° C. or higher by the total graph area is 5% or higher. Meanwhile, it can be seen that the final polymer according to Comparative Example 3 shows one peak at temperatures of 35° C. or higher, and the percentage value obtained by dividing the graph area at temperatures of 60° C. or higher by the total graph area is 3%. [Explanation of symbols]

[0150] 100 Slurry Polymerization Reaction 110 First slurry polymerization reaction 120 Second slurry polymerization reaction 200 Gas-phase polymerization reaction 210 First gas phase polymerization reaction 220 Second gas phase polymerization reaction

Claims

1. Contains a core portion and a shell portion, The density of the core portion is 0.857 g / cm ３ ~0.910g / cm ３ and The density of the shell portion is 0.890 g / cm ３ ~0.940g / cm ３ and A polyolefin polymer, wherein the density of the shell portion is higher than the density of the core portion.

2. The polyolefin polymer according to claim 1, wherein the polyolefin polymer has one or more of the following physical properties (a) to (h): (a) Melt flow index (MIE) from 0.1 g / 10 min to 5.0 g / 10 min (2.16 kg load, 190° C.) (b) 0.870g / cm ３ ~0.900g / cm ３ Density of (c) Two or more melting temperatures (T ｍ ) (d) First melting temperature (T ｍ１ ) and the second melting temperature (T ｍ２ ) and the difference between the first melting temperature and the second melting temperature is 30° C. to 70° C. (e) First melting temperature (T ｍ１ ) and the second melting temperature (T ｍ２ ) wherein the first melting temperature is between 45°C and 85°C and the second melting temperature is between 80°C and 125°C. (f) Two or more crystallization temperatures (T ｃ ) (g) First crystallization temperature (T ｃ１ ) and the second crystallization temperature (T ｃ２ ) wherein the first crystallization temperature is 40° C. to 100° C., and the second crystallization temperature is 70° C. to 110° C. (h) In a temperature rising elution fractionation (TREF) chromatogram, two or more peaks are shown at temperatures of 35°C or higher, and the percentage value obtained by dividing the graph area at 60°C or higher by the total graph area is 5% or higher.

3. The core has a density of 0.857 g / cm ３ ~0.910g / cm ３ and a melting temperature of 45° C. to 85° C.; The shell has a melt flow index (MIE (2.16 kg load, 190° C.)) of 0.01 g / 10 min to 5.0 g / 10 min and a density of 0.890 g / cm ３ ~0.940g / cm ３ It has a melting temperature of 80°C to 125°C and shows one peak at a temperature of 60°C or higher in a temperature rising elution fractionation chromatogram; 2. The polyolefin polymer according to claim 1, wherein a weight ratio of the core portion to the shell portion is from 40:60 to 90:

10.

4. one or more slurry polymerization reactors for slurry polymerization of a feed stream in the presence of a catalyst to produce a slurry reaction product comprising a prepolymer; one or more gas phase polymerization reactors that are fed the slurry reaction product, or the slurry reaction product and a feed stream, and that undergo a gas phase polymerization reaction to produce a gas phase reaction product comprising a final polymer, the feed stream comprises a monomer and a comonomer; The final polymer has two or more density distributions including a core portion and a shell portion having a higher density than the core portion, The operation temperature of the slurry polymerization reactor is 20° C. to 70° C., which is higher than the operation temperature of the gas phase polymerization reactor.

5. a first slurry polymerization reactor for slurry polymerization of the feed stream in the presence of the catalyst to produce a slurry reaction product comprising a prepolymer; a first gas phase polymerization reactor that is supplied with the slurry reaction product, or the slurry reaction product and a feed stream, and that undergoes a gas phase polymerization reaction to produce a gas phase reaction product comprising a final polymer.

6. a first slurry polymerization reactor for slurry polymerization of the feed stream in the presence of the catalyst to produce a first slurry reaction product comprising a prepolymer; a second slurry polymerization reactor that receives the first slurry reaction product, or the first slurry reaction product and a feed stream, from the first slurry polymerization reactor and performs a slurry polymerization reaction therein to produce a second slurry reaction product comprising a prepolymer; a first gas-phase polymerization reactor which receives the second slurry reaction product from the second slurry polymerization reactor, or the second slurry reaction product and a feed stream, and performs a gas-phase polymerization reaction therein to produce a first gas-phase reaction product comprising a final polymer; and a second gas phase polymerization reactor that receives the first gas phase reaction product from the first gas phase polymerization reactor, or the first gas phase reaction product and a feed stream, and performs a gas phase polymerization reaction to produce a second gas phase reaction product comprising a final polymer. The polyolefin polymerization system according to claim 4,

7. The polyolefin polymerization system of claim 4, wherein the catalyst is a metallocene monocatalyst.

8. 5. The polyolefin polymerization system of claim 4, wherein the monomer is ethylene.

9. 5. The polyolefin polymerization system according to claim 4, wherein the comonomer is at least one selected from the group consisting of 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, and 1-octene.

10. The operating temperature of the slurry polymerization reactor is 40° C. to 60° C. The polyolefin polymerization system according to claim 4, wherein the operating temperature of the gas phase polymerization reactor is 30°C to 50°C.

11. The gas phase polymerization reactor had an MIT temperature measured according to ASTM 3417-83. １５ 5. The polyolefin polymerization system of claim 4, which operates at a temperature below 15 wt. % melting initiation temperature.

12. the second gas phase polymerization reactor is operated in a high sorption mode; 7. The polyolefin polymerization system of claim 6, wherein the sorbent is used in the high sorption mode at 0.1 to 30 parts by weight per 100 parts by weight of the total recycle gas stream.

13. a slurry polymerization stage in which a feed composition comprising a monomer and a comonomer is subjected to one or more slurry polymerization reactions in the presence of a catalyst to produce a slurry reaction product comprising a prepolymer; a gas-phase polymerization step of subjecting the slurry reaction product obtained in the slurry polymerization step, or the slurry reaction product and a feed composition, to one or more gas-phase polymerization reaction to produce a gas-phase reaction product including a final polymer, The reaction temperature of the slurry polymerization step is 20° C. to 70° C., which is higher than the reaction temperature of the gas phase polymerization step; A method for polymerizing a polyolefin, wherein the final polymer has two or more density distributions including a core portion and a shell portion having a higher density than the core portion.

14. a slurry polymerization step of subjecting a feed composition comprising a monomer and a comonomer to a slurry polymerization reaction in the presence of the catalyst to produce a slurry reaction product comprising a prepolymer; The method for polymerizing polyolefins according to claim 13, further comprising: a gas-phase polymerization step of polymerizing the slurry reaction product obtained in the slurry polymerization step to produce a gas-phase reaction product including a final polymer.

15. a first slurry polymerization step of performing a first slurry polymerization reaction of a feed composition including a monomer and a comonomer in the presence of the catalyst to produce a first slurry reaction product including a prepolymer; a second slurry polymerization step of producing a second slurry reaction product including a prepolymer by subjecting the first slurry reaction product obtained in the first slurry polymerization step or the first slurry reaction product and a feed composition to a second slurry polymerization step; a first gas-phase polymerization step in which the second slurry reaction product obtained in the second slurry polymerization step or the second slurry reaction product obtained in the second slurry polymerization step and a feed composition are subjected to a primary gas-phase polymerization reaction to produce a first gas-phase reaction product including a final polymer; and a second gas-phase polymerization step of subjecting the first gas-phase reaction product obtained in the first gas-phase polymerization step, or the first gas-phase reaction product and a feed composition to a secondary gas-phase polymerization reaction to produce a second gas-phase reaction product comprising a final polymer.

16. The slurry polymerization reaction produces a prepolymer having a hollow structure to form the shell of the final polymer; 14. The process for polymerizing polyolefins according to claim 13, wherein the gas phase polymerization reaction fills the hollows of the prepolymer with a product of lower density than the prepolymer to form the core of the final polymer.

17. The density of the slurry was 0.890 g / cm3 through the second slurry polymerization step. ３ ~0.940g / cm ３ forming the shell portion; The density of the first gas phase polymerization step is 0.887 g / cm ３ ~0.898g / cm ３ forming the core portion; The density of the second gas phase polymerization step is 0.857 g / cm ３ ~0.886g / cm ３ The method for polymerizing polyolefins according to claim 15, wherein the core portion is formed of

18. 14. The method for polymerizing polyolefins according to claim 13, wherein the amount of the prepolymer produced is 10% by weight to 60% by weight based on the total amount of the final polymer produced.

19. The method for polymerizing polyolefins according to claim 13, wherein a molar ratio of the comonomer to the total amount of the monomer and the comonomer in the slurry polymerization step is 0.01 to 0.

3.

20. The method for polymerizing polyolefins according to claim 13, wherein a molar ratio of the comonomer to the total amount of the monomer and the comonomer in the gas phase polymerization step is 0.01 to 0.2.

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