Transition metal compound, catalyst composition, and method for preparing polypropylene by using same

Abstract

The present invention provides a transition metal compound, a catalyst composition, and a method for preparing polypropylene by using same, the transition metal compound having a narrow molecular weight distribution and a low weight average molecular weight and a high melt index such that polypropylene, which is useful for non-woven fabrics having a ultra-low basis weight characteristic and a high strength characteristic, can be prepared.

Description

Transition metal compound, catalyst composition, and method for producing polypropylene using the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0067859, filed May 24, 2024, and Korean Patent Application No. 10-2025-0067013, filed May 22, 2025, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a transition metal compound, a catalyst composition, and a method for producing polypropylene using the same, which can produce polypropylene having a narrow molecular weight distribution along with a low weight average molecular weight and a high melt index, thereby exhibiting excellent fiber spinnability and strength properties, and consequently being useful for nonwoven fabrics having ultra-low basis weight properties and high strength properties.

[0004]

[0005] Olefin polymerization catalyst systems can be classified into Ziegler-Natta and metallocene catalyst systems, and these two types of highly active catalyst systems have been developed according to their respective characteristics.

[0006] Ziegler-Natta catalysts have been widely applied in existing commercial processes since their invention in the 1950s. However, since they are multi-site catalysts with multiple active sites, they are characterized by a wide molecular weight distribution of polymers and an uneven distribution of comonomer composition, which limits the ability to secure desired properties.

[0007] On the other hand, metallocene catalysts are composed of a combination of a main catalyst mainly composed of a transition metal compound and a cocatalyst mainly composed of an organometallic compound composed of aluminum. Such catalysts are homogeneous complex catalysts and are single-site catalysts. Due to the single-site characteristics, a narrow molecular weight distribution is obtained, and a polymer with a uniform comonomer composition distribution is obtained. In addition, the stereoregularity, copolymerization characteristics, molecular weight, and crystallinity of the polymer can be changed by modifying the ligand structure of the catalyst and changing the polymerization conditions.

[0008] Recent shifts in environmental awareness have led many product groups to pursue reductions in volatile organic compounds (VOCs). However, Ziegler-Natta (Z / N) catalysts used in the production of polypropylene (PP) have been problematic for generating high TVOCs. While Ziegler-Natta catalysts are the dominant catalyst for commercially available polypropylene, the shift to metallocene catalysts, which offer lower odor and lower emission, is accelerating.

[0009] As global interest in sustainability grows, so too does the demand to reduce plastic use. One such demand is the reduction of disposable sanitary products, and one way to achieve this is to reduce the use of polymer fibers, which are primarily used in the manufacture of disposable sanitary products.

[0010] For polymer fibers, the basis weight can be controlled during nonwoven fabric manufacturing by varying the molecular weight distribution. A narrower molecular weight distribution exhibits superior spinnability and strength properties, allowing for a reduction in basis weight during nonwoven fabric manufacturing. Meltblown (M / B) nonwoven fabrics are polypropylene products with a very high melt index. For spinnability, a narrow molecular weight distribution (M / B) of 2.6 or less is typically required.

[0011] Accordingly, research is needed on a method for controlling the molecular weight distribution of polypropylene so as to reduce the basis weight during the manufacture of nonwoven fabrics.

[0012]

[0013] The present invention aims to provide a novel transition metal compound capable of producing polypropylene having a narrow molecular weight distribution along with a low weight average molecular weight and a high melt index, thereby exhibiting excellent fiber spinnability and strength properties, and as a result, being useful for producing nonwoven fabrics having ultra-low basis weight properties and high strength properties.

[0014] In addition, the present invention aims to provide a catalyst composition comprising the above transition metal compound, and a method for producing polypropylene using the same.

[0015]

[0016] The present invention provides a transition metal compound represented by the following chemical formula 1.

[0017] [Chemical Formula 1]

[0018]

[0019] In the above chemical formula 1,

[0020] M is a group 4 transition metal,

[0021] R1 and R1' are the same or different and are each independently C 1-20 Alkyl group, C 1-20 Alkoxy group, C 2-30 Alkoxyalkyl group, C 6-30 Aryl group, C 7-30 Arylalkyl group, and C 7-30 C substituted or unsubstituted with one or more substituents selected from the group consisting of alkylaryl groups 6-30 It is an aryl group,

[0022] R2 to R4, and R2' to R4' are the same or different, and each independently represents hydrogen, deuterium, C 1-30 Alkyl group, C 6-30 Aryl group, C 7-30 Arylalkyl group, or C 7-30It is an alkylaryl group,

[0023] R5 and R6 are the same or different and are each independently C 1-20 It is an alkyl group,

[0024] X1 and X2 are the same or different, and each independently represents a halogen group or C 1-20 It is an alkyl group,

[0025] n is an integer from 1 to 20.

[0026] The present invention also provides a catalyst composition comprising the above transition metal compound.

[0027] Furthermore, the present invention provides a method for producing polypropylene, comprising the step of polymerizing a propylene monomer in the presence of the catalyst composition.

[0028]

[0029] The transition metal compound according to the present invention has a narrow molecular weight distribution along with a low weight average molecular weight and a high melting index, and is useful for producing polypropylene exhibiting excellent fiber spinnability and strength properties.

[0030] In addition, polypropylene manufactured using the above transition metal compound or a catalyst composition containing the same has a narrow molecular weight distribution along with a low weight average molecular weight and a high melt index, and therefore can be used to manufacture a nonwoven fabric having ultra-low basis weight characteristics and high strength characteristics, particularly a low-brittleness fine-fiber meltblown nonwoven fabric.

[0031]

[0032] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the invention.

[0033] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0034] In this specification, the terms “comprise,” “include,” or “have” are intended to describe a feature, number, step, component, or combination thereof implemented, but do not exclude the possibility of one or more other features, numbers, steps, components, combinations, or additions thereof.

[0035] Additionally, the term “to” used in describing a numerical range in this specification includes both the upper and lower limits. For example, “1 to 3” means 1 or more and 3 or less.

[0036] Additionally, in this specification, ‘room temperature’ means 20±5℃.

[0037] The present invention is susceptible to various modifications and takes various forms. Specific embodiments are illustrated and described in detail below. However, this does not limit the invention to a specific disclosed form, but rather encompasses all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0038] Hereinafter, the transition metal compound, catalyst composition and method for producing polypropylene using the same according to the present invention will be described in detail.

[0039]

[0040] The transition metal compound according to the present invention is represented by the following chemical formula 1:

[0041] [Chemical Formula 1]

[0042]

[0043] In the above chemical formula 1,

[0044] M is a group 4 transition metal,

[0045] R1 and R1' are the same or different and are each independently C 1-20 Alkyl group, C 1-20 Alkoxy group, C 2-30 Alkoxyalkyl group, C 6-30 Aryl group, C7-30 Arylalkyl group, and C 7-30 C substituted or unsubstituted with one or more substituents selected from the group consisting of alkylaryl groups 6-30 It is an aryl group,

[0046] R2 to R4, and R2' to R4' are the same or different, and each independently represents hydrogen, deuterium, C 1-30 Alkyl group, C 6-30 Aryl group, C 7-30 Arylalkyl group, or C 7-30 It is an alkylaryl group,

[0047] R5 and R6 are the same or different and are each independently C 1-20 It is an alkyl group,

[0048] X1 and X2 are the same or different, and each independently represents a halogen group or C 1-20 It is an alkyl group,

[0049] n is an integer from 1 to 20.

[0050]

[0051] Unless otherwise specified in this specification, the following terms may be defined as follows:

[0052] A halogen can be fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).

[0053] C 1-20 The alkyl group (having 1 to 20 carbon atoms) may be a straight-chain, branched-chain or cyclic alkyl group. Specifically, C 1-20 The alkyl group is C 1-20 Straight-chain alkyl; C 1-12 Straight-chain alkyl; C 1-5 Straight-chain alkyl; C 3-20 Branched or cyclic alkyl; C 3-15 Branched or cyclic alkyl; or C 3-12 It may be a branched or cyclic alkyl group. More specifically, the C 1-20The alkyl group may include, but is not limited to, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, or a cyclooctyl group.

[0054] C 1-20 The alkoxy group of C may be a straight-chain, branched-chain or cyclic alkoxy group. Specifically, the C 1-20 Alkoxy group is C 1-20 Straight-chain alkoxy group; C 1-12 Straight-chain alkoxy; C 1-5 Straight-chain alkoxy group; C 3-20 Branched or cyclic alkoxy of C; 3-15 Branched or cyclic alkoxy of C; or 3-12 It can be a branched or cyclic alkoxy. More specifically, C 1-20 Examples of alkoxy groups include, but are not limited to, methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, iso-butoxy, tert-butoxy, n-pentoxy, iso-pentoxy, neo-pentoxy, or cyclohexene.

[0055] C 2-20 An alkoxyalkyl group may be a functional group in which one or more hydrogen atoms of the above-described alkyl group are replaced with alkoxy. More specifically, C 2-20 Examples of the alkoxyalkyl group include, but are not limited to, alkoxyalkyl groups such as a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, an iso-propoxymethyl group, an iso-propoxyethyl group, an iso-propoxypropyl group, an iso-propoxyhexyl group, a tert-butoxymethyl group, a tert-butoxyethyl group, a tert-butoxypropyl group, and a tert-butoxyhexyl group.

[0056] C 6-30 The aryl group may be a monocyclic, bicyclic, or tricyclic aromatic hydrocarbon. Specifically, C 6-30 Aryl group is C 6-18Aryl group, or C 6-12 It may be an aryl group. More specifically, the above C 6-30 Examples of aryl groups include, but are not limited to, phenyl, biphenyl, naphthyl, anthracenyl, phenanthrenyl, or fluorenyl.

[0057] C 7-30 An alkylaryl group means that at least one hydrogen atom of an aromatic ring is replaced by the alkyl group described above. Specifically, C 7-30 Alkylaryl group is C 7-20 Alkylaryl group, or C 7-14 It can be an alkylaryl group. More specifically, C 7-30 Examples of alkylaryl groups include, but are not limited to, methylphenyl, ethylphenyl, t-butylphenyl, methylbiphenyl, or methylnaphthyl.

[0058] C 7-30 An arylalkyl group may refer to a substituent in which one or more hydrogens of the above-described alkyl group are replaced by the above-described aryl group. Specifically, C 7-30 Arylalkyl group is C 7-20 Arylalkyl group, or C 7-14 It may be an arylalkyl group. More specifically, C 7-30 Examples of arylalkyl groups include, but are not limited to, phenylmethyl group, phenylethyl group, biphenylmethyl group, or naphthylmethyl group.

[0059] And, the group 4 transition metal may be titanium (Ti), zirconium (Zr), hafnium (Hf), or rutherfordium (Rf), specifically titanium (Ti), zirconium (Zr), or hafnium (Hf), but is not limited thereto.

[0060]

[0061] Meanwhile, the transition metal compound according to the present invention is as in the chemical formula 1, wherein the carbon at position 2 is substituted with an isopropyl group, and the carbon at position 4 is substituted with C 1-20 Alkyl group, C 1-20 Alkoxy group, C2-30 Alkoxyalkyl group, C 6-30 Aryl group, C 7-30 Arylalkyl group, and C 7-30 C substituted or unsubstituted with one or more substituents selected from the group consisting of alkylaryl groups 6-30 A compound having two indene structures substituted with aryl groups, wherein the indene structures are connected by a silicon bridging group. The silicon bridging group further includes a tether group of an alkoxyalkyl group including a long alkylene chain. Due to this characteristic structure, the transition metal compound exhibits excellent fiber spinnability and strength properties by having a narrow molecular weight distribution along with a low weight average molecular weight and a high melt index, and as a result, it is possible to produce a polypropylene useful for nonwoven fabrics having ultra-low basis weight properties and high strength properties, particularly for low brittleness and fine-grained meltblown nonwoven fabrics.

[0062] Specifically, the above transition metal compound can exhibit high structural stability as it has a structure in which two indene structures are connected by a bridging group as in the above chemical formula 1. In particular, when the two indene structures are substituted with the same substituent at the same position and have the same structure, the structural stability can be further enhanced.

[0063] In addition, when propylene and H2 are reacted together in a polymerization reaction for manufacturing polypropylene, the reaction occurs competitively. In the chemical formula 1, since the 2nd-position carbon of the indene structure is substituted with a bulky isopropyl group, a certain three-dimensional space arrangement (steric) is provided at the metal center, so that the reactivity of H2, which is smaller than propylene, is improved, and as a result, the hydrogen reactivity can be increased in the polymerization process. In addition, because it has high hydrogen reactivity, a high melting index product (high MI PP) can be produced even with a small amount of hydrogen.

[0064] In addition, a substituent (R1 and R1') having an electron-donating effect on the 4th position carbon of the above indene structure, specifically C 1-20 Alkyl group, C 1-20 Alkoxy group, C 2-30 Alkoxyalkyl group, C 6-30 Aryl group, C 7-30 Arylalkyl group, and C 7-30 C substituted or unsubstituted with one or more substituents selected from the group consisting of alkylaryl groups 6-30 By including an aryl group, electrons can be abundantly provided to the Group 4 transition metal atom included in the bridge structure of the above chemical formula 1. As a result, the cationic properties of the Group 4 transition metal M are increased, thereby improving catalytic activity and increasing the reaction rate, so that polypropylene having a higher molecular weight can be produced during a polymerization reaction under the same conditions.

[0065] Also, the above C 6-30 Aryl group, C 1-20 Alkyl group, C 1-20 Alkoxy group, C 2-30 Alkoxyalkyl group, C 6-30 Aryl group, C 7-30 Arylalkyl group, and C 7-30 When substituted with one or more substituents selected from the group consisting of alkylaryl groups, electrons can be more abundantly supplied to the aryl group through an inductive effect. In addition, by increasing the overall size of the transition metal compound and thereby increasing the available angle, the approach of monomers can be facilitated, thereby exhibiting improved catalytic activity.

[0066] In addition, the above transition metal compound can exhibit high structural stability because it supplies electrons to the group 4 transition metal M in a form in which two indene structures are connected by a bridge group.

[0067] In addition, the bridge group includes an alkoxyalkyl tether group that can act as a Lewis base as an oxygen-donor. Due to this tether group, the catalyst precursor can be chemically bonded to the carrier and supported, and as a result, the catalyst precursor can be prevented from being released from the carrier during the polymerization process, thereby ensuring process stability. In particular, if the catalyst precursor is leached, a phenomenon such as fouling in which polymers stick to each other on the surface of the reactor during polymerization occurs, but the transition metal compound has excellent bonding performance with the carrier during the production of the supported catalyst, and can minimize the leaching phenomenon in which the precursor is separated from the carrier during the polymerization process of propylene, etc., and as a result, it improves the process stability along with the catalyst activity during the polymerization of propylene, and can significantly reduce process troubles (reactor fouling, plugging) even during long-term production.

[0068] Specifically, in the above chemical formula 1, M may be titanium (Ti), zirconium (Zr), or hafnium (Hf).

[0069] Also, specifically in the chemical formula 1, R1 and R1' are the same or different from each other, and each independently represents C 1-12 Alkyl group, C 1-12 Alkoxy group, C 2-20 Alkoxyalkyl group, C 6-20 Aryl group, C 7-20 Arylalkyl group, and C 7-20 C substituted or unsubstituted with one or more substituents selected from the group consisting of alkylaryl groups 6-18 It can be an aryl group. More specifically, R1 and R1' are the same, and C 1-6 Straight-chain alkyl group, C 3-6 Branched alkyl group, C 1-6 Straight-chain alkoxy group, C 3-6 Branched-chain alkoxy group, and C 6-12 C substituted or unsubstituted with one or more substituents selected from the group consisting of aryl groups 6-12It may be an aryl group. More specifically, R1 and R1' are the same and may be a t-butylphenyl group, a 2,4-di-t-butylphenyl group, methylphenyl, isopropoxyphenyl, or biphenyl.

[0070] In addition, in the above chemical formula 1, specifically, R2 to R4 and R2' to R4' can each be hydrogen.

[0071] Also, in the above chemical formula 1, specifically R5 is C 3-12 It is a branched alkyl group, and R6 is C 1-6 Straight-chain alkyl group or C 3-6 It may be a branched alkyl group. More specifically, R5 may be a t-butyl group and R6 may be a methyl group.

[0072] In addition, in the above chemical formula 1, specifically, X1 and X2 may be the same as or different from each other, and may each independently be a chloro or methyl group.

[0073] Also, in the above chemical formula 1, specifically, n may be an integer from 1 to 20. More specifically, n may be an integer of 1 or more, or 2 or more, or 4 or more, and 20 or less, or 12 or less, or 10 or less, or 8 or less, or 6 or less.

[0074] More specifically, the transition metal compound may be any one of the compounds represented by the following chemical formulas 1-1 to 1-6:

[0075] (1-1) (1-2)

[0076] (1-3) (1-4)

[0077] (1-5) (1-6)

[0078]

[0079] The transition metal compound represented by the above chemical formula 1 can be synthesized by applying known reactions.

[0080] For example, the transition metal compound may be prepared by a method including a step (Step 1) of reacting an indene compound (i) with a halogenated silane compound (Silane) as a bridging group-providing raw material to prepare a ligand compound (ii) in which two indenyls are connected by a silicon bridging group, as in the following reaction scheme 1; and a step (Step 2) of reacting the ligand compound (ii) with a halogen salt (Metal halide) of a Group 4 transition metal to prepare a transition metal compound (1) of the above chemical formula 1. The following reaction scheme 1 is merely an example for explaining the present invention, and the present invention is not necessarily limited thereto.

[0081] [Reaction Formula 1]

[0082]

[0083] In the above reaction scheme 1, each substituent is as defined above, and X is a halogen element.

[0084] Specifically, the method for preparing the transition metal compound according to one embodiment of the invention may include a step (Step 1) of reacting an indene compound (i), such as 2-isopropyl-4-tert-butylphenylindene, with a halogenated silane compound, such as (6-t-butoxyhexyl)dichloromethylsilane or (6-t-butoxybutyl)dichloromethylsilane, as a bridging group-providing raw material, in the presence of an alkyl lithium, such as n-butyllithium (n-BuLi), to prepare a ligand compound (ii); and a step (Step 2) of reacting the ligand compound (ii) with a halogen salt (metal halide) of a Group 4 transition metal, such as ZrCl4, to prepare a transition metal compound (1) of the chemical formula 1.

[0085] Meanwhile, according to the present invention, a catalyst composition comprising the above transition metal compound is provided.

[0086] Specifically, the catalyst composition may include the transition metal compound as a single component.

[0087] In addition, the catalyst composition may further include at least one of a carrier and a cocatalyst together with the transition metal compound.

[0088] When further comprising a carrier, the catalyst composition may be in the form of a supported metallocene catalyst. When a supported metallocene catalyst is used, the resulting polypropylene has excellent morphology and physical properties, and can be suitably used in conventional slurry polymerization, bulk polymerization, or gas phase polymerization processes.

[0089] Specifically, the carrier may include silica, a silica-alumina composite, or a silica-magnesia composite, and one or a mixture of two or more thereof may be used. In addition, the carrier may be a carrier having a highly reactive hydroxyl group, silanol group, or siloxane group on the surface, and for this purpose, a carrier that has been surface-modified by calcination or whose surface has had moisture removed by drying may be used.

[0090] Among the above-mentioned carriers, in the case of silica, since the silica carrier and the functional group of the compound of the above-mentioned chemical formula 1 are chemically bonded and supported, there is almost no catalyst liberated from the surface of the carrier during the propylene polymerization process, and as a result, fouling caused by adhesion of the reactor wall or polymer particles to each other can be minimized when manufacturing polypropylene through slurry or gas phase polymerization.

[0091] In addition, when supported on a carrier, the compound of the above formula 1 can be supported in a content range of 10 μmol or more, 12 μmol or more, or 14 μmol or more, and 30 μmol or less, or 20 μmol or less, or 16 μmol or less, based on the weight of the carrier, for example, about 1 g of silica. When supported in the above content range, it is advantageous for the production of polypropylene.

[0092] In addition, when the catalyst composition further includes a cocatalyst, the cocatalyst may specifically include one or more of the compounds represented by the following chemical formulas 2 to 4.

[0093] [Chemical Formula 2]

[0094] -[Al(R 22 )-O] m -

[0095] In the above chemical formula 2,

[0096] R 22 are identical or different from each other, and each independently represents a halogen group, C 1-20 Alkyl group or C 1-20 is a haloalkyl group;

[0097] m is an integer greater than or equal to 2;

[0098] [Chemical Formula 3]

[0099] J(R 23 )3

[0100] In the above chemical formula 3,

[0101] R 23 are identical or different from each other, and each independently represents a halogen group, C 1-20 Alkyl group or C 1-20 is a haloalkyl group;

[0102] J is aluminum or boron;

[0103] [Chemical Formula 4]

[0104] [EH] + [ZQ4] -

[0105] In the above chemical formula 4,

[0106] E is a neutral or cationic Lewis base;

[0107] H is a hydrogen atom;

[0108] Z is a group 13 element;

[0109] Q are identical or different and each independently represents C 6-20 Aryl group or C 1-20is an alkyl group, wherein the C 6-20 Aryl group or C 1-20 The alkyl group is unsubstituted or substituted with a halogen group, C 1-20 Alkyl group, C 1-20 Alkoxy group and C 6-20 It is substituted with one or more substituents selected from the group consisting of aryloxy groups.

[0110] Examples of the compound represented by the above chemical formula 2 include aluminoxane compounds such as methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, or butylaluminoxane, and any one of these or a mixture of two or more thereof may be used.

[0111] Examples of the compound represented by the above chemical formula 3 include trimethylaluminum, triethylaluminum, triisobutylaluminum, tripropylaluminum, tributylaluminum, dimethylchloroaluminum, triisopropylaluminum, tri-s-butylaluminum, tricyclopentylaluminum, tripentylaluminum, triisopentylaluminum, trihexylaluminum, trioctylaluminum, ethyldimethylaluminum, methyldiethylaluminum, triphenylaluminum, tri-p-tolylaluminum, dimethylaluminum methoxide, dimethylaluminum ethoxide, trimethylboron, triethylboron, triisobutylboron, tripropylboron, tributylboron, etc., and more specifically, it may be selected from trimethylaluminum, triethylaluminum, and triisobutylaluminum. there is.

[0112] Examples of compounds represented by the above chemical formula 4 include triethylammonium tetraphenylboron, tributylammonium tetraphenylboron, trimethylammonium tetraphenylboron, tripropylammonium tetraphenylboron, trimethylammonium tetra(p-tolyl)boron, trimethylammonium tetra(o,p-dimethylphenyl)boron, tributylammonium tetra(p-trifluoromethylphenyl)boron, trimethylammonium tetra(p-trifluoromethylphenyl)boron, tributylammonium tetrapentafluorophenylboron, N,N-diethylanilinium tetraphenylboron, N,N-diethylanilinium tetrapentafluorophenylboron, diethylammonium tetrapentafluorophenylboron, triphenylphosphonium tetraphenylboron, trimethylphosphonium tetraphenylboron, triethylammonium tetraphenylaluminum, tributylammonium tetraphenylaluminum, trimethylammonium tetraphenylaluminum, Tripropylammonium tetraphenylaluminum, trimethylammonium tetra(p-tolyl)aluminum, tripropylammonium tetra(p-tolyl)aluminum, triethylammonium tetra(o,p-dimethylphenyl)aluminum, tributylammonium tetra(p-trifluoromethylphenyl)aluminum, trimethylammonium tetra(p-trifluoromethylphenyl)aluminum, tributylammonium tetrapentafluorophenylaluminum, N,N-diethylanilinium tetraphenylaluminum, N,N-diethylanilinium tetrapentafluorophenylaluminum, diethylammonium tetrapentatetraphenylaluminum, triphenylphosphonium tetraphenylaluminum, trimethylphosphonium tetraphenylaluminum, tripropylammonium tetra(p-tolyl)boron, triethylammonium tetra(o,p-dimethylphenyl)boron, Examples thereof include tributylammonium tetra(p-trifluoromethylphenyl)boron, triphenylcarbonium tetra(p-trifluoromethylphenyl)boron, or triphenylcarbonium tetrapentafluorophenylboron, and any one of these or a mixture of two or more thereof may be used.

[0113] Among the above-mentioned cocatalysts, the compound of the above-mentioned chemical formula 2 can be used in terms of improving catalytic activity when used with the compound of the above-mentioned chemical formula 1. More specifically, the cocatalyst can be used by adding an alkyl aluminoxane such as methylaluminoxane. The alkylaluminoxane-based cocatalyst acts as a scavenger for hydroxyl groups present on the surface of the carrier, thereby improving catalytic activity, and converts the halogen group of the catalyst precursor into a methyl group, thereby promoting the growth of polypropylene chains.

[0114] The above-mentioned cocatalyst may be supported in an amount of 1 mmol or more or 2 mmol or more per weight of the carrier, for example, based on 1 g of silica, and may also be supported in an amount of 10 mmol or less or 5 mmol or less. When included in the above-mentioned content range, the use of the cocatalyst may exhibit an effect of improving catalytic activity.

[0115] The degree of loading varies depending on the degree of defects between the carrier and the transition metal compound in the catalyst composition. When the loading of the transition metal compound, which is the catalyst precursor, is not securely achieved, leaching occurs during the polymerization process, in which the catalyst precursor falls off the carrier. If such a phenomenon exists, the stability of the polymerization process is significantly deteriorated, causing process troubles (reactor fouling, plugging) during long-term production. In response to this, the transition metal compound of the above chemical formula 1 has an optimized structure and substituent characteristics, and thus forms a high bonding force with the carrier, thereby significantly reducing the leaching of Group 4 transition metals such as Ti and Zr, and as a result, excellent process stability can be maintained even during long-term production. In addition, polypropylene with controlled physical properties can be easily manufactured.

[0116] Accordingly, the present invention provides a method for producing polypropylene, comprising the step of polymerizing a propylene monomer in the presence of the catalyst composition.

[0117] The above polymerization reaction can be carried out by single polymerization of propylene using a continuous slurry polymerization reactor, a loop slurry reactor, a gas phase reactor or a solution reactor.

[0118] And, the temperature during the polymerization reaction may be 20°C or higher, or 50°C or higher, or 70°C or higher, and 200°C or lower, or 150°C or lower, or 120°C or lower.

[0119] In addition, the pressure during the polymerization reaction may be 10 bar or more, or 15 bar or more, or 20 bar or more, and 50 bar or less, or 40 bar or less, or 35 bar or less.

[0120] In addition, the above-described catalyst composition may be introduced into the polymerization reaction as it is, or may be introduced after being dissolved or diluted in a solvent. Examples of the solvent include aliphatic hydrocarbon solvents having 5 to 12 carbon atoms, such as pentane, hexane, heptane, nonane, and decane; aromatic hydrocarbon solvents such as toluene and benzene; or hydrocarbon solvents substituted with one or more chlorine atoms, such as dichloromethane and chlorobenzene; and the like. One or a mixture of two or more of these may be used. In addition, the solvent may be treated with a small amount of alkyl aluminum to remove a small amount of water or air, which act as catalyst poisons in the solvent, before use.

[0121] As described above, the transition metal compound according to the present invention exhibits excellent hydrogen reactivity when used as a polymerization catalyst for producing polypropylene. Accordingly, even with a small amount of hydrogen input, polypropylene having a high melt index (MI), e.g., an MI of 200.0 g / 10 min to 1000.0 g / 10 min, suitable for producing fibers or nonwoven fabrics can be produced.

[0122] For example, during the polymerization reaction, hydrogen gas may be introduced in an amount of 0.1 to 30 vol% based on the total volume of the propylene monomer. More specifically, the hydrogen gas may be introduced in an amount of 0.1 vol% or more, or 1 vol% or more, or 5 vol% or more, or 10 vol% or more, and 30 vol% or less, or 25 vol% or less, or 20 vol% or less, or 15 vol% or less, based on the total weight of the propylene monomer.

[0123] Additionally, the polymerization reaction may be a homopolymerization reaction in which a propylene monomer is polymerized alone. Accordingly, the polypropylene according to the present invention may be a homopolymer.

[0124] The polypropylene according to the present invention manufactured by the above polymerization reaction exhibits a narrow molecular weight distribution along with a low weight average molecular weight and a high melting index.

[0125] Specifically, the polypropylene may satisfy all of the following conditions (i) to (iii):

[0126] (i) Molecular weight distribution: 2.60 or less

[0127] (ii) Weight average molecular weight: 50,000 to 100,000 g / mol

[0128] (iii) Melting index measured at 230℃ and 2.16kg according to ASTM D1238: 200.0 to 1,000.0 g / 10min.

[0129] Specifically, the polypropylene has a narrow molecular weight distribution (Mw / Mn) of 2.60 or less. As such, by having a narrow molecular weight distribution, it exhibits excellent spinning properties and strength properties, and as a result, an ultra-low basis weight is possible when manufacturing fibers or nonwoven fabrics, particularly when manufacturing melt-blown nonwoven fabrics. More specifically, the polypropylene may have a molecular weight distribution of 2.60 or less, or 2.55 or less, or 2.52 or less, or 2.50 or less, or 2.30 or less. The lower limit of the molecular weight distribution is not particularly limited, but may be, for example, 1.00 or more, or 1.50 or more, or 2.00 or more, or 2.10 or more, or 2.15 or more, or 2.18 or more.

[0130] In addition, the polypropylene has a low weight average molecular weight of 50,000 to 100,000 g / mol. Due to such a low Mw, it can exhibit a high melting index, and as a result, it can exhibit improved fiber spinnability or fiber processability along with excellent rigidity. Specifically, the polypropylene may have a weight average molecular weight of 50,000 g / mol or more, or 60,000 g / mol or more, or 70,000 g / mol or more, or 75,000 g / mol or more, and 100,000 g / mol or less, or 90,000 g / mol or less, or 87,000 g / mol or less.

[0131] Meanwhile, in the present invention, the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of polypropylene are measured using gel permeation chromatography (GPC, manufactured by Water), and then the molecular weight distribution is calculated as the ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn). Here, the weight average molecular weight (Mw) and number average molecular weight (Mn) are polystyrene-converted molecular weights analyzed by GPC. The specific measurement method is as described in the experimental examples below.

[0132] In addition, the above polypropylene has a melt index (MI) 2.16 )(ASTM D1238, 230℃, 2.16kg) is high at 200.0 to 1,000.0 g / 10min. As it exhibits such a high melting index, it can exhibit excellent strength properties, and as a result, it can exhibit ultra-low basis weight properties and excellent strength properties when manufacturing nonwoven fabrics, especially melt-blown nonwoven fabrics. Specifically, the MI of the polypropylene 2.16 may be 200.0 g / 10min or more, or 400.0 g / 10min or more, or 500.0 g / 10min or more, or 600.0 g / 10min or more, or 650.0 g / 10min or more, and 1,000.0 g / 10min or less, or 800.0 g / 10min or less, or 750.0 g / 10min or less, or 710.0 g / 10min or less.

[0133] The polypropylene according to the present invention, which simultaneously satisfies the above-mentioned physical property requirements, exhibits high rigidity along with excellent fiber spinnability compared to conventional Ziegler-Natta catalyst-applied polypropylene, conventional metallocene catalyst-applied homopolypropylene or propylene copolymer, or polybutene. Accordingly, it is possible to produce ultra-low basis weight and high rigidity nonwoven fabrics, particularly low brittle fine-fiber meltblown nonwoven fabrics, which can reduce the amount of plastic used in diapers and the like.

[0134]

[0135] Hereinafter, the functions and effects of the invention will be described in more detail through specific examples. However, these examples are provided merely as examples of the invention and do not define the scope of the invention.

[0136] <Preparation of Transition Metal Compounds>

[0137] Synthesis Example 1

[0138]

[0139] Step 1: Ligand synthesis

[0140] 2-Isopropyl-4-tert-butylphenylindene (15.0 g, 51.6 mmol) was dissolved in a toluene / THF=1 / 1 solution (172 mL), and n-butyllithium solution (2.5 M, hexane solvent, 22.7 mL) was slowly added dropwise at 0°C, and the mixture was stirred at room temperature for 4 hours. Then, (6-t-butoxyhexyl)dichloromethylsilane (7.40 g) was slowly added dropwise to the above mixed solution at -78°C, stirred for about 10 minutes, and then stirred at room temperature for 1 day. After that, water was added to separate the organic layer, and the solvent was distilled under reduced pressure to obtain (6-t-butoxyhexyl)(methyl)-bis(2-isopropyl-4-tert-butyl-phenylindenyl)silane.

[0141]

[0142] Step 2: Synthesis of transition metal compounds

[0143] To the dried ligand, 43 mL of toluene and 21.5 mL of Et2O were added and stirred. The resulting reaction product was cooled to -78°C, and n-BuLi (2.5 M, 22.7 mL) was slowly added dropwise while stirring. After the addition of n-BuLi was complete, the resulting mixture was stirred at room temperature for approximately 4 hours, cooled to -20°C, and a solution of ZrCl4 (6 g) dissolved in toluene was added thereto. The resulting mixture was stirred at 25°C for 12 hours and then dried to remove the solvent. The resulting dried product was added to THF, stirred, and then vacuum-dried. The resulting product was filtered using dichloromethane (DCM), dried, and recrystallized using toluene / hexane. As a result, the transition metal compound (1-1) of the above structure was obtained as a yellow powder (yield: 35%).

[0144] 1H NMR (500 MHz, CDCl3) δ 7.69 - 7.54 (m, 5H), 7.47 (dd, J = 11.5, 4.8 Hz, 5H), 7.35 (d, J = 6.9 Hz, 2H), 7.09 (ddd, J = 8.7, 7.0, 3.8 Hz, 2H), 7.00 (s, 2H), 3.38 (t, J = 6.5 Hz, 2H), 3.26 - 3.09 (m, 2H), 2.07 - 1.79 (m, 3H), 1.75 - 1.45 (m, 7H), 1.44 - 1.29 (m, 22H), 1.20 (s, 9H), 1.16 - 1.04 (m, 12H).

[0145]

[0146] Synthesis Example 2

[0147] (1-2)

[0148] In step 1 of the above Synthesis Example 1, except that (6-t-butoxybutyl)dichloromethylsilane was used instead of (6-t-butoxyhexyl)dichloromethylsilane, the same method as in the above Synthesis Example 1 was performed to prepare a transition metal compound (1-2) having the above structure.

[0149] 1H NMR (500 MHz, CDCl3) δ 7.62 (m, J = 8.6 Hz, 5H), 7.54 (m, J = 8.7 Hz, 1H), 7.47 (m, J = 7.9 Hz, 4H), 7.36 (d, J = 6.9 Hz, 2H), 7.10 (q, J = 7.9 Hz, 2H), 7.01 (s, 2H), 3.51 (t, J = 6.1 Hz, 2H), 3.29 - 3.13 (m, 2H), 2.12 - 1.79 (m, 5H), 1.73 - 1.61 (m, 1H), 1.37 (d, J = 17.2 Hz, 22H), 1.26 - 1.21 (m, 9H), 1.12 (t, J = 7.2 Hz, 12H).

[0150]

[0151] Synthesis Example 3

[0152] (1-3)

[0153] In step 1 of the above Synthetic Example 1, except that 2-isopropyl-4-methyl-phenylindene was used instead of 2-isopropyl-4-t-butylphenylindene and (6-t-butoxybutyl)dichloromethylsilane was used instead of (6-t-butoxyhexyl)dichloromethylsilane, the same method as in the above Synthetic Example 1 was performed to prepare a transition metal compound (1-3) having the above structure.

[0154] 1H NMR (500 MHz, CDCl3) δ 7.50 (d, J = 8.9 Hz, 1H), 7.43 (m, 5H), 7.23 (m, 2H), 7.15 (S, 3H), 7.14 (s, 2H), 6.99 (m, 2H), 6.85 (d, J = 4.0 Hz, 2H), 3.39 (t, J = 6.3 Hz, 2H), 3.08 (m, 2H), 2.27 (s, 6H), 1.96 - 1.91 (m, 1H), 1.87 - 1.82 (m, 2H), 1.79 - 1.74 (m, 2H), 1.58 - 1.52 (m, 1H), 1.27 (s, 3H), 1.13 (S, 9H), 1.02 - 0.98 (m, 12H).

[0155]

[0156] Synthesis Example 4

[0157] (1-4)

[0158] In step 1 of the above Synthetic Example 1, except that 2-isopropyl-4-isopropoxy-phenylindene was used instead of 2-isopropyl-4-t-butylphenylindene and (6-t-butoxybutyl)dichloromethylsilane was used instead of (6-t-butoxyhexyl)dichloromethylsilane, the same method as in the above Synthetic Example 1 was performed to prepare a transition metal compound (1-4) having the above structure.

[0159] 1H NMR (500 MHz, CDCl3) δ 7.62 - 7.51 (m, 6H), 7.34 - 7.32 (m, 2H), 7.13 - 7.07 (m, 2H), 7.01 - 6.96 (m, 6H), 4.59 (m, 2H), 3.51 (t, J = 6.3 Hz, 2H), 3.22 (m, 2H), 2.07 - 2.00 (m, 1H), 1.99 - 1.94 (m, 2H), 1.92 - 1.86 (m, 2H), 1.39 - 1.36 (m, 16H), 1.25 (s, 9H), 1.15 - 1.10 (m, 12H)

[0160]

[0161] Synthesis Example 5

[0162] (1-5)

[0163] In step 1 of the above Synthetic Example 1, except that 2-isopropyl-4-(2,4-dimethyl-phenyl)indene was used instead of 2-isopropyl-4-t-butylphenylindene and (6-t-butoxybutyl)dichloromethylsilane was used instead of (6-t-butoxyhexyl)dichloromethylsilane, the same method as in the above Synthetic Example 1 was performed to prepare a transition metal compound (1-5) having the above structure.

[0164] 1H NMR (500 MHz, CDCl3) δ 7.63 (d, J = 6.9 Hz, 1H), 7.57 (m, 4H), 7.54 (d, 2H), 7.42 - 7.40 (m, 4H), 7.13 - 7.08 (m, 2H), 7.03 (s, 2H), 3.51 (t, J = 6.3 Hz, 2H), 3.25 - 3.16 (m, 2H), 2.09 - 1.85 (m, 6H), 1.39 (s, 6H), 1.32 (s, 36H), 1.24 (s, 9H), 1.12 - 1.08 (m, 12H)

[0165]

[0166] Synthesis Example 6

[0167] (1-6)

[0168] In step 1 of the above Synthetic Example 1, except that 2-isopropyl-4-biphenylindene was used instead of 2-isopropyl-4-t-butylphenylindene and (6-t-butoxybutyl)dichloromethylsilane was used instead of (6-t-butoxyhexyl)dichloromethylsilane, the same method as in the above Synthetic Example 1 was performed to prepare a transition metal compound (1-6) having the above structure.

[0169] 1H NMR (500 MHz, CDCl3) δ 7.63 - 7.61 (m, 4H), 7.58 - 7.54 (m, 6H), 7.51 - 7.50 (m, 4H), 7.44 (d, 1H), 7.32 - 7.28 (m, 6H), 7.24 - 7.19 (m, 2H), 7.02 - 6.98 (m, 2H), 6.90 (d, 2H), 3.38 (t, J = 6.3 Hz, 2H), 3.09 (m, 2H), 1.95 - 1.90 (m, 1H), 1.88 - 1.82 (m, 2H), 1.79 - 1.73 (m, 2H), 1.58 - 1.52 (m, 1H), 1.27 (s, 3H), 1.12 (s, 9H), 1.02 - 0.99 (m, 12H)

[0170]

[0171] Example 1

[0172] Preparation of catalyst composition

[0173] After 32 mL of toluene was added to a pico reactor, 5 g of silica was transferred. 10 mmol of methylaluminoxane (MAO) was added to the reactor and reacted at 90°C for 24 hours. After the resulting reaction product was precipitated, the supernatant was separated and removed, and the remaining precipitate was washed twice with toluene. 70 μmol of the transition metal compound (1-1) prepared in Synthesis Example 1 was dissolved in toluene, added to the washed product, and reacted at 50°C for 3 hours. After the reaction was completed and the reaction product precipitated, the supernatant was separated and removed, and the remaining precipitate was washed with toluene. Thereafter, the precipitate was washed again with hexane, 3 wt% of Atmer was added under hexane, and stirred for 10 minutes. After stirring, when the reaction product precipitated, the supernatant was separated and removed, and the remaining precipitate was vacuum-dried to obtain a catalyst composition in the form of solid particles.

[0174]

[0175] Manufacturing of polypropylene

[0176] A stainless steel reactor was purged with Ar, and 1.5 mL of triethylaluminum, 20 mL of hydrogen, and 200 mL of propylene were sequentially added at room temperature. The amount of hydrogen gas added corresponds to 10% by volume based on the total volume of propylene monomer. After stirring for 10 minutes, the catalyst composition prepared above was introduced into the reactor under nitrogen pressure. After polymerization was performed for 30 minutes at a polymerization pressure of approximately 30 bar and a polymerization temperature of 70°C, unreacted propylene was vented.

[0177] In the production of the above polypropylene, the catalyst activity (Activity, kgPP / gCat·hr) was calculated as the ratio of the weight of polymer produced (kg PP) per weight (g) of the catalyst composition used per unit time (hr). As a result, the catalyst composition exhibited a catalyst activity of 2.95 kgPP / gCat·hr.

[0178]

[0179] Example 2

[0180] A catalyst composition and polypropylene were prepared in the same manner as in Example 1, except that the transition metal compound (1-2) prepared in Synthesis Example 2 was used instead of the transition metal compound (1-1) in preparing the catalyst composition in Example 1. In addition, the catalytic activity of the catalyst composition calculated in the same manner as in Example 1 was 2.39 kgPP / gCat·hr.

[0181]

[0182] Example 3

[0183] A catalyst composition and polypropylene were prepared in the same manner as in Example 1, except that the transition metal compound (1-3) prepared in Synthesis Example 3 was used instead of the transition metal compound (1-1) in preparing the catalyst composition in Example 1. In addition, the catalytic activity of the catalyst composition calculated in the same manner as in Example 1 was 2.09 kgPP / gCat·hr.

[0184]

[0185] Example 4

[0186] A catalyst composition and polypropylene were prepared in the same manner as in Example 1, except that the transition metal compound (1-4) prepared in Synthesis Example 4 was used instead of the transition metal compound (1-1) in preparing the catalyst composition in Example 1. In addition, the catalytic activity of the catalyst composition calculated in the same manner as in Example 1 was 1.10 kgPP / gCat·hr.

[0187]

[0188] Example 5

[0189] A catalyst composition and polypropylene were prepared in the same manner as in Example 1, except that the transition metal compound (1-5) prepared in Synthesis Example 5 was used instead of the transition metal compound (1-1) in preparing the catalyst composition in Example 1. In addition, the catalytic activity of the catalyst composition calculated in the same manner as in Example 1 was 2.31 kgPP / gCat·hr.

[0190]

[0191] Example 6

[0192] A catalyst composition and polypropylene were prepared in the same manner as in Example 1, except that the transition metal compound (1-6) prepared in Synthesis Example 6 was used instead of the transition metal compound (1-1) in preparing the catalyst composition in Example 1. In addition, the catalytic activity of the catalyst composition calculated in the same manner as in Example 1 was 2.13 kgPP / gCat·hr.

[0193]

[0194] Comparative Example 1

[0195] A catalyst composition and polypropylene were manufactured in the same manner as in Example 1, except that a transition metal compound (a) having the following structure was used instead of the transition metal compound (1-1) in the manufacture of the catalyst composition in Example 1.

[0196] (a)

[0197]

[0198] Comparative Example 2

[0199] A catalyst composition and polypropylene were manufactured in the same manner as in Example 1, except that a transition metal compound (b) having the following structure was used instead of the transition metal compound (1-1) in the manufacture of the catalyst composition in Example 1.

[0200] (b)

[0201]

[0202] Comparative Example 3

[0203] A catalyst composition and polypropylene were manufactured in the same manner as in Example 1, except that a transition metal compound (c) having the following structure was used instead of the transition metal compound (1-1) in the manufacture of the catalyst composition in Example 1.

[0204] (c)

[0205]

[0206] Comparative Example 4

[0207] A catalyst composition and polypropylene were manufactured in the same manner as in Example 1, except that a transition metal compound (d) having the following structure was used instead of the transition metal compound (1-1) in the manufacture of the catalyst composition in Example 1.

[0208] (d)

[0209]

[0210] Comparative Example 5

[0211] A catalyst composition and polypropylene were manufactured in the same manner as in Example 1, except that a transition metal compound (e) having the following structure was used instead of the transition metal compound (1-1) in the manufacture of the catalyst composition in Example 1.

[0212] (e)

[0213]

[0214] Experimental example

[0215] The physical properties of the polypropylene manufactured in the above examples and comparative examples were measured, and the results are shown in Table 1.

[0216] (1) Weight average molecular weight (Mw) and molecular weight distribution (MWD)

[0217] The weight average molecular weight (Mw, g / mol) and number average molecular weight (Mn, g / mol) of polypropylene were measured through gel permeation chromatography (GPC) analysis, and the molecular weight distribution (MWD = Mw / Mn) was obtained by dividing the weight average molecular weight measured above by the number average molecular weight.

[0218] Specifically, a Waters PL-GPC220 gel permeation chromatography (GPC) device and a Polymer Laboratories PLgel MIX-B 300 mm column were used. The measurement temperature was 160°C, 1,2,4-trichlorobenzene was used as the solvent, and the flow rate was 1 mL / min. Each sample of the polypropylene prepared above was pretreated by dissolving it in 1,2,4-trichlorobenzene containing 0.0125% BHT at 160°C for 3 hours using a GPC analysis device (PL-GPC220), and then preparing it at a concentration of 10 mg / 10 mL, and then supplying it in an amount of 200 μL. The values ​​of Mw and Mn were derived using a calibration curve formed using polystyrene standard samples. The weight average molecular weights of the polystyrene standard specimens were 9 types: 2,000 g / mol, 10,000 g / mol, 30,000 g / mol, 70,000 g / mol, 200,000 g / mol, 700,000 g / mol, 2,000,000 g / mol, 4,000,000 g / mol, and 10,000,000 g / mol.

[0219]

[0220] (2) Melting index (MI) 2.16 )

[0221] The melt index was measured (g / 10 min) according to ASTM D1238 (condition E, 230 ℃, 2.16 kg load).

[0222]

[0223] Transition metal compound type H2 input amount (mL) Mw (g / mol) MW DMI (g / 10 min) Example 1 Compound 1-1 2086, 795 2.186 57.1 Example 2 Compound 1-2 2075, 640 2.277 0 1.3 Example 3 Compound 1-3 2073, 571 2.52 75 0.4 Example 4 Compound 1-4 2096, 371 2.50 600 Example 5 Compound 1-5 2080, 795 2.49 68 2.4 Example 6 Compound 1-6 2085, 387 2.47 66 0.7 Comparative Example 1 Compound a 20277, 685 2.81 1.7 Comparative Example 2 Compound Comparative Example 3 Compound b20126,0002.38121.9 Comparative Example 3 Compound c20250,0002.8010 Comparative Example 4 Compound d20273,2182.8512.01 Comparative Example 5 Compound e20325,6632.652.8

[0224]

[0225] As a result of the experiment, the polypropylene manufactured using the catalyst compositions of Examples 1 to 6, each of which includes the transition metal compounds manufactured in Synthetic Examples 1 to 6, exhibited a narrow molecular weight distribution of 2.60 or less despite a low weight average molecular weight and a high melt index. From this, it can be expected that the polypropylene exhibits excellent spinning properties during fiber spinning and also has improved strength properties, which is advantageous for manufacturing nonwoven fabrics having high strength along with ultra-low basis weight properties when manufacturing disposable sanitary materials such as diapers.

[0226] Meanwhile, polypropylenes manufactured using the catalyst compositions of Comparative Examples 1, 3, 4 and 5, each comprising transition metal compounds (a), (c), (d) and (e) in which the second-position carbon in the two indenyl structures is substituted with methyl, exhibited a broad molecular weight distribution along with a high weight-average molecular weight and a low melt index. From this, it can be expected that the polypropylenes of Comparative Examples 1, 3, 4 and 5 have deteriorated spinning properties and low strength properties, and as a result, it can be expected that it will be difficult to manufacture nonwoven fabrics with ultra-low basis weight and high strength.

[0227] In addition, polypropylene manufactured using the catalyst composition of Comparative Example 2 containing a transition metal compound (b) in which one of the two indenyl structures has its 2-position carbon substituted with an isopropyl group and the other has its methyl substituted, exhibited a narrow molecular weight distribution, but had a high weight average molecular weight and a low melting index, so it can be expected that it will be difficult to manufacture a nonwoven fabric with ultra-low basis weight and high strength.

[0228] From the above experimental results, it can be seen that the transition metal compound according to the present invention has a narrow molecular weight distribution of 2.60 or less along with a low weight average molecular weight and a high melting index, thereby exhibiting excellent fiber spinnability and strength properties, and as a result, it can produce polypropylene useful for nonwoven fabrics having ultra-low basis weight properties and high strength properties.

Claims

1. A transition metal compound represented by the following chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, M is a group 4 transition metal, R1 and R1' are the same or different and are each independently C 1-20 Alkyl group, C 1-20 Alkoxy group, C 2-30 Alkoxyalkyl group, C 6-30 Aryl group, C 7-30 Arylalkyl group, and C 7-30 C substituted or unsubstituted with one or more substituents selected from the group consisting of alkylaryl groups 6-30 It is an aryl group, R2 to R4, and R2' to R4' are the same or different, and each independently represents hydrogen, deuterium, C 1-30 Alkyl group, C 6-30 Aryl group, C 7-30 Arylalkyl group, or C 7-30 It is an alkylaryl group, R5 and R6 are the same or different and are each independently C 1-20 It is an alkyl group, X1 and X2 are the same or different, and each independently represents a halogen group or C 1-20 It is an alkyl group, n is an integer from 1 to 20.

2. In paragraph 1, M is titanium, zirconium or hafnium, Transition metal compounds.

3. In paragraph 1, R1 and R1' are the same or different and are each independently C 1-12 Alkyl group, C 1-12 Alkoxy group, C 2-20 Alkoxyalkyl group, C 6-20 Aryl group, C 7-20 Arylalkyl group, and C 7-20 C substituted or unsubstituted with one or more substituents selected from the group consisting of alkylaryl groups 6-18 Aryl group, Transition metal compounds.

4. In paragraph 1, R1 and R1' are identical, C 1-6 Straight-chain alkyl group, C 3-6 Branched alkyl group, C 1-6 Straight-chain alkoxy group, C 3-6 Branched-chain alkoxy group, and C 6-12 C substituted or unsubstituted with one or more substituents selected from the group consisting of aryl groups 6-12 Aryl group, Transition metal compounds.

5. In paragraph 1, R1 and R1' are the same as each other and are t-butylphenyl group, 2,4-di-t-butylphenyl group, methylphenyl, isopropoxyphenyl, or biphenyl, Transition metal compounds.

6. In paragraph 1, R2 to R4, and R2' to R4' are each hydrogen, Transition metal compounds.

7. In paragraph 1, R5 is C 3-12 It is a branched alkyl group, R6 is C 1-6 A straight-chain or branched-chain alkyl group, Transition metal compounds.

8. In paragraph 1, R5 is a t-butyl group, R6 is a methyl group, Transition metal compounds.

9. In paragraph 1, X1 and X2 are the same or different and each independently represent a chloro or methyl group, Transition metal compounds.

10. In paragraph 1, n is an integer from 1 to 6, Transition metal compounds.

11. In paragraph 1, The above transition metal compound is any one of the compounds represented by the following chemical formulas 1-1 to 1-6: Transition metal compounds: (1-1) (1-2) (1-3) (1-4) (1-5) (1-6).

12. A catalyst composition comprising the transition metal compound of paragraph 1.

13. In paragraph 12, Further comprising at least one of a cocatalyst and a carrier, Catalytic composition.

14. In paragraph 13, The above cocatalyst is selected from the group consisting of compounds represented by the following chemical formulas 2 to 4. Catalyst composition: [Chemical Formula 2] -[Al(R 22 )-O] m - In the above chemical formula 2, R 22 are identical or different from each other, and each independently represents halogen, C 1-20 Alkyl group or C 1-20 is a haloalkyl group; m is an integer greater than or equal to 2; [Chemical Formula 3] J(R 23 )3 In the above chemical formula 3, R 23 are identical or different from each other, and each independently represents a halogen group, C 1-20 Alkyl group or C 1-20 is a haloalkyl group; J is aluminum or boron; [Chemical Formula 4] [E-H] + [ZQ4] - In the above chemical formula 4, E is a neutral or cationic Lewis base; H is a hydrogen atom; Z is a group 13 element; Q are identical or different and each independently represents C 6-20 Aryl group or C 1-20 is an alkyl group, wherein the C 6-20 Aryl group or C 1-20 The alkyl group is unsubstituted or substituted with a halogen group, C 1-20 Alkyl group, C 1-20 Alkoxy group and C 6-20 It is substituted with one or more substituents selected from the group consisting of aryloxy groups.

15. In paragraph 13, The carrier comprises silica, a silica-alumina composite, a silica-magnesia composite or a mixture thereof. Catalytic composition.

16. A method for producing polypropylene, comprising the step of polymerizing a propylene monomer in the presence of a catalyst composition according to claim 12.

17. In paragraph 16, The above polymerization is performed by adding hydrogen gas at 0.1 to 30 volume% based on the total volume of propylene monomer. Method for producing polypropylene.

18. In paragraph 16, The above polypropylene satisfies the conditions (i) to (iii) below: Method for manufacturing polypropylene: (i) Molecular weight distribution: 2.60 or less (ii) Weight average molecular weight: 50,000 to 100,000 g / mol (iii) Melting index measured at 230℃ and 2.16kg according to ASTM D1238: 200.0 to 1,000.0 g / 10min.

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