Polypropylene resin composition and polypropylene fiber prepared using same

Abstract

The invention provides a polypropylene resin composition suitable for ultra-low basis weight and high-rigidity non-woven fabrics and polypropylene fibers prepared from the polypropylene resin composition. Wherein optimized melt index, melting point and crystallization temperature and narrow molecular weight distribution are obtained by using a polypropylene resin prepared in the presence of a metallocene compound having a specific structure and a molecular weight modifier within predetermined ranges.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based upon and claims the benefit of priority from Korean Patent Application Nos. 10-2023-0028621 and 10-2024-0029138, filed on March 3, 2023, and February 28, 2024, respectively, the disclosures of which are incorporated herein in their entirety by reference.

[0003] The invention relates to a polypropylene resin composition suitable for ultra-low basis weight, high-rigidity non-woven fabrics, and polypropylene fibers prepared therefrom. Background Art

[0004] Generally, nonwoven refers to the fabric made by mechanical and chemical treatment (such as mechanical operation or thermal bonding) by bonding or interlocking fiber aggregates without spunbonding, weaving or knitting processes.Nonwoven includes felt, resin bonded nonwoven, needle punched nonwoven, spunbond nonwoven, spunlace nonwoven, embossed film, wet nonwoven etc. In a narrow sense, it means that the contact points between the randomly stacked net and the fiber are bonded together by resin and used as interwoven fabric etc.Nonwoven is called bonded fabric, also referred to as bonded fabric.These nonwovens can be produced by several methods, and known needle punching, chemical bonding, thermal bonding, meltblown, spunlace, seam bonding and spunbond are provided.

[0005] Spunbond nonwoven fabrics using polyolefin resins as raw materials are excellent in terms of touch, flexibility, air permeability, thermal insulation, etc., and are therefore widely used in filters, packaging materials, bedding, clothing, medical supplies, sanitary products, automotive interior materials, construction materials, etc. In particular, polypropylene fibers, due to their inherent low melting point and excellent chemical resistance, are processed into thermally bonded nonwoven fabrics by a calender bonding method or by an air bonding method, and are mainly used as surface materials for sanitary products such as diapers and sanitary napkins.

[0006] At the same time, due to the recent environmental protection trend, the demand for reducing the use of plastics in diapers and the like is growing, and the demand for improving the toughness is increasing to reduce the weight of spunbond nonwoven fabrics in diaper construction. Therefore, metallocene catalyst-based homopolypropylene products are applied to existing spunbond nonwoven fabrics to improve the toughness.

[0007] Generally, the catalyst systems mainly used for polypropylene polymerization can be divided into Ziegler-Natta catalyst systems and metallocene catalyst systems, and these two highly active catalyst systems have been developed based on their characteristics. Since its development in the 1950s, Ziegler-Natta catalysts have been widely used in existing commercial processes. However, since Ziegler-Natta catalysts are multi-active site catalysts with multiple active sites mixed therein, they are characterized by a polymer having a wide molecular weight distribution, and due to the uneven distribution of the composition of the comonomer, there is a problem that it is difficult to obtain the desired physical properties.

[0008] In addition, metallocene catalysts are composed of a main catalyst having a transition metal compound as the main component and an organometallic compound cocatalyst having aluminum as the main component. This catalyst is a single-site catalyst, which is a homogeneous composite catalyst. Due to its single-site characteristics, it provides polymers with a narrow molecular weight distribution and a uniform composition distribution of comonomers. The stereoregularity, copolymerization characteristics, molecular weight, crystallinity, etc. of the polymer can be controlled by changing the ligand structure of the catalyst and the polymerization conditions.

[0009] In the case of polypropylene resins, which are primarily used to make spunbond nonwovens, the toughness of the filaments is generally determined by the orientation and crystallinity of the polypropylene polymer chains. In the case of homopolypropylene resins, the toughness of spunbond nonwovens can generally be increased by increasing their weight-average molecular weight.

[0010] However, as the molecular weight of the homopolypropylene resin increases, the risk of single yarn failure during spinning due to phenomena such as melt fracture and draw resonance increases, making it difficult to ensure stable processability during spinning.

[0011] In particular, to further improve the toughness of polypropylene resins used to manufacture ultra-low basis weight, high-stiffness nonwoven fabrics, which are a recent trend, the molecular weight distribution must be further narrowed compared to products using conventional technologies. However, due to limitations in catalyst technology, the level of improvement is limited. Therefore, it is not possible to improve fiber toughness compared to the current level.

[0012] Therefore, there is a need to develop a polypropylene resin composition and fiber suitable for ultra-low basis weight, high-rigidity nonwoven fabrics that can reduce the use of plastics in diapers and the like in light of recent environmental issues. Summary of the Invention

[0013] Technical issues

[0014] Provided is a polypropylene resin composition in which the melt index, melting point and crystallization temperature are all optimized together with a narrow molecular weight distribution by controlling a polypropylene prepared in the presence of a metallocene compound having a specific structure and a molecular weight modifier within a predetermined range.

[0015] In another embodiment of the present invention, a method for preparing the polypropylene resin composition is provided.

[0016] In another embodiment of the present invention, fibers and spunbonded nonwoven fabrics produced using the polypropylene resin composition are provided.

[0017] Technical Solution

[0018] According to one embodiment of the present invention, there is provided a polypropylene resin composition, wherein the molecular weight distribution (Mw / Mn) is 1.7 or more and 2.35 or less, and the melt index (MI measured at 230° C. under a load of 2.16 kg) is 1.7 or more and 2.35 or less. 2.16 ) is from 18 g / 10 min to 36 g / 10 min both inclusive, the melting point (Tm) is from 135° C. to 135° C., and the crystallization temperature (Tc) is from 115° C. to 115° C. both inclusive.

[0019] According to other embodiments of the present invention, a method for preparing the polypropylene resin composition is also provided.

[0020] According to another embodiment of the present invention, there are also provided polypropylene fibers and spunbonded nonwoven fabrics, each comprising the polypropylene resin composition.

[0021] Beneficial effects

[0022] In the polypropylene resin composition according to the present invention, the melt index, melting point, and crystallization temperature, as well as the narrow molecular weight distribution, are all optimized by using polypropylene prepared in the presence of a metallocene compound having a specific structure and a molecular weight modifier within a predetermined range. Therefore, the polypropylene resin composition is advantageous for producing spunbond nonwoven fabrics having high tenacity and ultra-low basis weight characteristics, thereby minimizing weight when used in diapers and the like. DETAILED DESCRIPTION

[0023] In the present invention, the terms used herein are only used to explain exemplary embodiments and are not intended to limit the present invention.

[0024] Unless the context indicates otherwise, a singular expression may include a plural expression.

[0025] In the present invention, it should be understood that the terms "including", "equipped with" or "having" in this specification are only used to indicate the existence of functional characteristics, numbers, steps, components or their combinations, and do not exclude the existence or possibility of one or more different characteristics, numbers, steps, components or their combinations added in advance.

[0026] In the present invention, when a layer or element is referred to as being formed "on" or "over" a layer or element, it means that each layer or element is directly formed on the layer or element, or other layers or elements may be additionally formed between the layers, or on a body or substrate.

[0027] The present invention can be modified in various ways and has various forms, and specific exemplary embodiments will be described and described in detail below. However, it should be understood that this description is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is intended to cover all modifications, equivalents and alternatives that fall within the spirit and scope of the invention.

[0028] Hereinafter, a polypropylene resin composition according to a specific embodiment of the present invention, a preparation method thereof, and a fiber comprising the composition will be described in detail.

[0029] Polypropylene resin composition

[0030] According to one embodiment of the present invention, there is provided a polypropylene resin composition characterized in that all the above requirements are met, wherein the molecular weight distribution (Mw / Mn) is 1.7 or more and 2.35 or less, and the melt index (MI measured at 230°C under a load of 2.16 kg) is 1.7 or more and 2.35 or less. 2.16 ) is from 18 g / 10 min to 36 g / 10 min both inclusive, the melting point (Tm) is from 135° C. to 135° C., and the crystallization temperature (Tc) is from 115° C. to 115° C. both inclusive.

[0031] In the present invention, when preparing a polypropylene resin composition (which can be used to manufacture fibers, particularly high-tenacity yarns suitable for ultra-low basis weight, high-rigidity non-woven fabrics that can reduce the use of plastics in diapers, etc. in response to recent environmental issues), polypropylene prepared in the presence of a metallocene compound having a specific structure and a molecular weight modifier are used within a predetermined range. As a result, the resin composition having all optimized physical properties in terms of melt index, melting point, and crystallization temperature, as well as a narrow molecular weight distribution, can significantly increase the draw ratio during fiber processing, thereby exhibiting high tenacity and excellent processability suitable for ultra-low basis weight, high-rigidity non-woven fabrics that can reduce the use of plastics in diapers, etc. in response to recent environmental issues.

[0032] Specifically, the polypropylene resin composition has a molecular weight distribution (Mw / Mn, MWD) of more than 1.7 to less than 2.35. More specifically, the molecular weight distribution (Mw / Mn, MWD) of the polypropylene resin composition is more than 1.75, or more than 1.78, or more than 1.8, or more than 1.82, or more than 1.85, or more than 1.88, or more than 1.9, or more than 1.92, or more than 1.95, and less than 2.34, or less than 2.33, or less than 2.32, or less than 2.31, or less than 2.3, or less than 2.28. The polypropylene resin composition has a narrow molecular weight distribution of less than 2.35, thereby having increased rigidity and showing excellent mechanical properties when manufacturing fiber products for multifilament or spunbond. In addition, when the polypropylene resin composition has a too low molecular weight distribution less than 1.7, due to poor spinning during fiber manufacturing, the problem of processability deterioration may occur.

[0033] In one embodiment of the present invention, the molecular weight distribution can be obtained by measuring the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polypropylene resin composition using gel permeation chromatography (GPC), respectively, and calculating the ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn).

[0034] Specifically, Waters' PL-GPC220 can be used as a gel permeation chromatography (GPC) instrument, and a Polymer Laboratories PLgel MIX-B 300mm length column can be used. The measuring temperature is 160°C, and 1,2,4-trichlorobenzene can be used as a solvent and applied at a flow rate of 1mL / min. Each polypropylene sample can be pretreated by being dissolved in 1,2,4-trichlorobenzene containing 0.0125% BHT at 160°C for 10 hours using a GPC analyzer (PL-GP220), and the sample is prepared at a concentration of 10mg / 10mL and supplied in an amount of 200μL. Mw and Mn values ​​can be obtained using a calibration curve formed by a polystyrene standard sample. Nine polystyrene standard samples were used, whose molecular weights were 2000 g / mol, 10000 g / mol, 30000 g / mol, 70000 g / mol, 200000 g / mol, 700000 g / mol, 2000000 g / mol, 4000000 g / mol, and 100000000 g / mol, respectively.

[0035] In addition, the weight average molecular weight of the polypropylene resin composition may be 150,000 g / mol or more, or 150,000 g / mol to 230,000 g / mol. Specifically, the weight average molecular weight of the polypropylene resin composition may be 155,000 g / mol or more, or 160,000 g / mol or more, or 165,000 g / mol or more, or 170,000 g / mol or more, and 225,000 g / mol or less, or 220,000 g / mol or less, or 215,000 g / mol or less, or 210,000 g / mol or less.

[0036] At the same time, the polypropylene resin composition exhibits an optimized melt index and a narrow molecular weight distribution (MWD), thereby being used to produce fibers suitable for spunbond nonwoven fabrics having high stiffness and ultra-low basis weight characteristics so as to minimize the content relative to the application volume when used in diapers, etc.

[0037] Specifically, the melt index (MI measured at 230° C. under a load of 2.16 kg) of the polypropylene resin composition is as measured at 230° C. under a load of 2.16 kg according to the American Society for Testing and Materials standard ASTM D 1238. 2.16 ) is from 18 g / 10 min to 36 g / 10 min. More specifically, the melt index (MI) of the polypropylene resin composition is 2.16 ) may be 19 g / 10 min or more, or 20 g / 10 min or more, or 22 g / 10 min or more, or 24 g / 10 min or more, or 25 g / 10 min or more, or 28 g / 10 min or more, and 35.5 g / 10 min or less, or 35 g / 10 min or less, or 34.5 g / 10 min or less, or 34 g / 10 min or less, or 33.5 g / 10 min or less, or 33 g / 10 min or less, or 32.5 g / 10 min or less, or 32 g / 10 min or less. Here, in terms of providing high tenacity during fiber manufacturing, the melt index (MI) of the polypropylene resin composition is preferably 2.16 ) should be 18g / 10min or more. However, when the melt index (MI) of the polypropylene resin composition 2.16 ) becomes too high exceeding 36 g / 10 min, the viscosity and molecular weight of the resin composition may decrease, which may lead to a problem of deterioration of toughness during fiber production.

[0038] For example, the melt index (MI measured at 230°C under a load of 2.16 kg) of the polypropylene resin composition 2.16) may be 22 g / 10 min or more and 27 g / 10 min or less, or 23.5 g / 10 min or more and 26.5 g / 10 min or less, or 24 g / 10 min or more and 25 g / 10 min or less, and the molecular weight distribution (Mw / Mn) may be 1.85 or more and 2.35 or less, or 1.88 or more and 2.34 or less, or 1.9 or more and 2.33 or less. In addition, the melt index (MI measured at 230° C. under a load of 2.16 kg) of the polypropylene resin composition is 2.16 ) can be from 30 g / 10 min to 36 g / 10 min, or from 32 g / 10 min to 35.5 g / 10 min, or from 33 g / 10 min to 35 g / 10 min, and the molecular weight distribution (Mw / Mn) can be from 1.7 to 2.3, or from 1.75 to 2.28, or from 1.85 to 2.26.

[0039] At the same time, as described above, the polypropylene resin composition has an optimized molecular weight distribution (MWD) and melt index, and simultaneously has a melting point (Tm) and crystallization temperature (Tc) within an optimal range, thereby producing fibers suitable for spunbond nonwoven fabrics having high tenacity and ultra-low basis weight characteristics, which can minimize the use of plastics when used in diapers, etc.

[0040] Specifically, the polypropylene resin composition may have a melting point (Tm) of 135°C or higher, or 135°C to 155°C, and a crystallization temperature (Tc) of 115°C or lower, or 95°C to 115°C or lower.

[0041] More specifically, the melting point (Tm) of the polypropylene resin composition may be 136° C. or higher, or 138° C. or higher, or 140° C. or higher, or 142° C. or higher, or 145° C. or higher, or 148° C. or higher, or 150° C. or higher, and 154.5° C. or lower, or 154° C. or lower, or 153.5° C. or lower, or 153° C. or lower, or 152.5° C. or lower, or 152° C. or lower. In particular, the melting point (Tm) of the polypropylene resin composition should be 135° C. or higher in terms of ensuring excellent mechanical properties (such as high tenacity) and excellent heat resistance during fiber manufacturing.

[0042] In addition, the crystallization temperature (Tc) of the polypropylene resin composition may be 113.5° C. or less, or 113° C. or less, or 112.5° C. or less, or 112° C. or less, or 111.5° C. or less, or 111° C. or less, or 111.5° C. or less, or 110° C. or less, and 96° C. or more, or 98° C. or more, or 100° C. or more, or 102° C. or more, or 105° C. or more. In particular, the crystallization temperature (Tc) of the polypropylene resin composition should be 115° C. or less in terms of preventing spinning defects due to rapid viscosity increase and excessive solidification of spun filaments during fiber production.

[0043] In one embodiment of the present invention, melting point (Tm) and crystallization temperature (Tc) can be measured using a differential scanning calorimeter (DSC, such as device name: DSC 2920, manufacturer: TAinstrument). Specifically, the temperature is raised to heat the polypropylene polymer to 200°C and then maintained at this temperature for 5 minutes. Then, the temperature is reduced to 30°C, and when the temperature is raised again, the temperature corresponding to the peak value of the DSC (differential scanning calorimeter, manufactured by TA) curve is determined as the melting point (Tm). Thereafter, when the temperature is reduced to 30°C again, the peak value of the curve is determined as the crystallization temperature (Tc). At this time, the heating and cooling rates are 10°C / min, and the melting point (Tm) and crystallization temperature (Tc) are represented by the results measured in the second heating and cooling cycle.

[0044] As described above, compared with existing polypropylene using a Ziegler-Natta catalyst or homopolypropylene, propylene copolymer, polybutene, etc. using a conventional metallocene catalyst, the polypropylene resin composition of the present invention has excellent process stability and workability as well as high stiffness, and at the same time can obtain characteristics suitable for ultra-low basis weight, high stiffness non-woven fabrics, which can reduce the use of plastics in diapers, etc. in response to recent environmental issues.

[0045] In the resin composition of the present invention, one or more additives may be used within a range that does not impair the properties of the resin composition, such as antioxidants, lubricants, UV stabilizers, neutralizers, dispersants, weathering agents, antistatic agents, UV stabilizers, slip agents, antiblocking agents, talc, nucleating agents, etc. More specifically, one or more additives selected from the group consisting of antioxidants, lubricants, UV stabilizers, and neutralizers may be used as additives.

[0046] Preparation method of polypropylene resin composition

[0047] Meanwhile, according to another embodiment of the present invention, a method for preparing a polypropylene resin composition having the physical properties as described above is provided.

[0048] In the present invention, a method for preparing a polypropylene resin composition includes the following steps: preparing a polypropylene resin by polymerizing propylene monomer in the presence of a catalyst composition and hydrogen, wherein the catalyst composition includes one or more metallocene compounds represented by the following Chemical Formula 1; and melt-extruding a mixture comprising the polypropylene resin and a molecular weight modifier under the conditions of 120° C. to 300° C., wherein the content of the molecular weight modifier is 210 ppm to 940 ppm based on the weight of the polypropylene resin.

[0049] [Chemical Formula 1]

[0050]

[0051] In Chemical Formula 1,

[0052] A is carbon, silicon or germanium,

[0053] M is zirconium or hafnium,

[0054] X1 and X2 are each independently halogen,

[0055] R1 and R5 are each independently substituted with C 1-20 C of alkyl 6-20 Aryl,

[0056] R2 to R4 and R6 to R8 are each independently hydrogen, halogen, C 1-20 Alkyl, C 2-20 Alkenyl, C 1-20 Alkylsilyl, C 1-20 Silylalkyl, C 1-20 Alkoxysilyl, C 1-20 Ether, C 1-20 Silyl ether, C 1-20 Alkoxy, C 6-20 Aryl, C 7-20 Alkyl aryl or C 7-20 Arylalkyl,

[0057] R9 is replaced by C 1-20 Alkoxy or unsubstituted C 1-20 alkyl, and

[0058] R 10 It is C 1-20 Alkyl or C 2-20 Alkenyl.

[0059] Unless otherwise specified herein, the following terms may be defined as follows.

[0060] The halogen may be fluorine (F), chlorine (Cl), bromine (Br) or iodine (I).

[0061] Alkyl groups having 1 to 20 carbon atoms (i.e., C 1-20 The alkyl group) may be a straight chain, branched or cyclic alkyl group. Specifically, the alkyl group having 1 to 20 carbon atoms may be a straight chain alkyl group having 1 to 20 carbon atoms; a straight chain alkyl group having 1 to 15 carbon atoms; a straight chain alkyl group having 1 to 5 carbon atoms; a branched or cyclic alkyl group having 3 to 20 carbon atoms; a branched or cyclic alkyl group having 3 to 15 carbon atoms; or a branched or cyclic alkyl group having 3 to 10 carbon atoms. For example, an alkyl group having 1 to 20 carbon atoms (C 1-20 ) can be methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, etc., but is not limited thereto.

[0062] Alkenyl groups having 2 to 20 carbon atoms (i.e., C 2-20 The alkenyl group) may be a linear or branched alkenyl group, and specifically, may include allyl, ethenyl, propenyl, butenyl, pentenyl, etc., but is not limited thereto.

[0063] Alkoxy groups having 1 to 20 carbon atoms (i.e., C 1-20 The alkoxy group) may include methoxy, ethoxy, isopropoxy, n-butoxy, tert-butoxy, phenoxy, cyclohexyloxy, etc., but is not limited thereto.

[0064] Alkoxyalkyl having 2 to 20 carbon atoms (i.e., C 2-20 The alkoxyalkyl group may be a functional group in which one or more hydrogen atoms of the alkyl group as described above are replaced by an alkoxy group, and specifically, may include alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, isopropoxymethyl, isopropoxyethyl, isopropoxypropyl, isopropoxyhexyl, tert-butoxymethyl, tert-butoxyethyl, tert-butoxypropyl, tert-butoxyhexyl, etc., but are not limited thereto. Aryloxyalkyl groups may include phenoxyhexyl, etc., but are not limited thereto.

[0065] Alkylsilyl having 1 to 20 carbon atoms (i.e., C 1-20 alkylsilyl) or an alkoxysilyl group having 1 to 20 carbon atoms (C 1-20The alkoxysilyl group) may be a functional group in which 1 to 3 hydrogens of -SiH3 are replaced by 1 to 3 alkyl or alkoxy groups as described above, and specifically, may include an alkylsilyl group such as a methylsilyl group, a dimethylsilyl group, a trimethylsilyl group, a dimethylethylsilyl group, a diethylmethylsilyl group or a dimethylpropylsilyl group, etc.; an alkoxysilyl group such as a methoxysilyl group, a dimethoxysilyl group, a trimethoxysilyl group or a dimethoxyethoxysilyl group; an alkoxyalkylsilyl group such as a methoxydimethylsilyl group, a diethoxymethylsilyl group or a dimethoxypropylsilyl group, etc., but is not limited thereto.

[0066] Silylalkyl having 1 to 20 carbon atoms (i.e., C 1-20 The silylalkyl group may be a functional group in which one or more hydrogens of the alkyl group as described above are substituted with a silyl group, and specifically, may include -CH2-SiH3, methylsilylmethyl or dimethylethoxysilylpropyl, etc., but is not limited thereto.

[0067] In addition, an alkylene group having 1 to 20 carbon atoms (i.e., C 1-20 The alkylene group is the same as the above-mentioned alkyl group, except that it is a divalent substituent, and specifically, it can include methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, cycloheptylene, cyclooctylene and the like, but is not limited thereto.

[0068] An aryl group having 6 to 20 carbon atoms (i.e., C 6-20 Aryl) may refer to monocyclic, bicyclic or tricyclic aromatic hydrocarbons. For example, aryl may include phenyl, biphenyl, naphthyl, anthracenyl, phenanthrenyl, fluorenyl, etc., but is not limited thereto.

[0069] Alkylaryl groups having 7 to 20 carbon atoms (i.e., C 7-20 Alkylaryl) may refer to a substituent in which one or more hydrogen atoms of an aromatic ring are replaced by an alkyl group as described above. For example, alkylaryl may include methylphenyl, ethylphenyl, methylbiphenyl, methylnaphthyl, etc., but is not limited thereto.

[0070] In addition, an arylalkyl group having 7 to 20 carbon atoms (i.e., C 7-20 Arylalkyl) may refer to a substituent in which one or more hydrogen atoms of the above-mentioned alkyl group are replaced by the above-mentioned aryl group. For example, arylalkyl may include phenylmethyl, phenylethyl, biphenylmethyl, naphthylmethyl, etc., but is not limited thereto.

[0071] In addition, an arylene group having 6 to 20 carbon atoms (i.e., C 6-20The arylene group is the same as the above-mentioned aryl group except that it is a divalent substituent, and specifically, may include phenylene, biphenylene, naphthylene, anthrylene, phenanthrenylene, fluorenylene, etc., but is not limited thereto.

[0072] In addition, the Group 4 transition metal may be titanium (Ti), zirconium (Zr), hafnium (Hf) or rhodium (Rf), particularly titanium (Ti), zirconium (Zr) or hafnium (Hf), and more particularly zirconium (Zr) or hafnium (Hf), but is not limited thereto.

[0073] In addition, the Group 13 element may be boron (B), aluminum (Al), gallium (Ga), indium (In), or thallium (Tl), particularly boron (B) or aluminum (Al), but is not limited thereto.

[0074] The above substituents may be optionally substituted with one or more substituents selected from the group consisting of: hydroxyl; halogen; alkyl or alkenyl, aryl, alkoxy; alkyl or alkenyl, aryl, alkoxy containing one or more heteroatoms from Groups 14 to 16; silyl; alkylsilyl or alkoxysilyl; phosphino; phosphide group; sulfonate group; and sulfone group, the substituents being within the range of achieving the same to similar effects as the desired effect.

[0075] The catalyst composition for preparing the polypropylene resin composition according to one embodiment of the present invention is characterized by including a metallocene compound represented by Chemical Formula 1. In particular, when a metallocene catalyst having a specific substituent in a bridge group connecting two ligands containing indenyl groups is used, polypropylene can be prepared in which the melt index, melting point and crystallization temperature, and molecular weight distribution are all optimized to meet desired physical properties.

[0076] Furthermore, since the compound of Chemical Formula 1 includes a divalent functional group A disubstituted with the same alkyl group having two or more carbon atoms as a bridging group connecting two indenyl-containing ligands, the atomic size increases and the available angle increases, so the monomers are more accessible, resulting in more excellent catalytic activity.

[0077] Furthermore, two indenyl groups as ligands in the compound of Chemical Formula 1 are respectively substituted with methyl groups at their 2-positions and respectively include aryl groups substituted with alkyl groups at their 4-positions (ie, R1 and R5), thereby exhibiting more excellent catalytic activity through an inductive effect of providing sufficient electrons.

[0078] More specifically, in Chemical Formula 1, R1 and R5 can each independently be substituted with C 1-10 C of alkyl 6-12 Aryl, and more specifically, C 3-6The phenyl group of the branched alkyl group is, for example, tert-butylphenyl. In particular, the substitution position of the alkyl group on the phenyl group may be the 4-position corresponding to the para position of the position on R1 and R5 to which the indenyl group is bonded.

[0079] For example, R1 and R5 are phenyl substituted with tert-butyl. More preferably, R1 and R5 are 4-tert-butylphenyl.

[0080] In addition, in Chemical Formula 1, R2 to R4 and R6 to R8 may each independently be hydrogen, and X1 and X2 may each independently be chlorine (Cl).

[0081] In addition, in Chemical Formula 1, A may be silicon (Si). In addition, in terms of improving the loading efficiency by increasing the solubility, R9 and R 10 is a substituent of A, R9 may be substituted with C 3-6 Alkoxy-substituted or unsubstituted C 1-10 Alkyl, and R 10 Can be C 1-10 Specifically, R9 can be 6-tert-butoxy-hexyl, R 10 It can be methyl, or R9 and R 10 Both can be ethyl.

[0082] In addition, in Chemical Formula 1, M may be zirconium (Zr). In particular, when the compound of Chemical Formula 1 includes zirconium (Zr) as a central metal, it has more orbitals capable of accepting electrons compared to those containing another Group 4 element (e.g., hafnium (Hf)). Therefore, it can bind to the monomer with higher affinity, thereby exhibiting significantly improved catalytic activity.

[0083] Furthermore, the metallocene compound may specifically be, for example, any one of the compounds having the following structural formulas:

[0084]

[0085] The compounds having the above-mentioned structural formula are merely examples for explaining the present invention, and the present invention is not limited thereto.

[0086] In addition, the metallocene compound represented by Chemical Formula 1 can be prepared by a known method of synthesizing an organic compound, and will be described in more detail in Examples described later.

[0087] Meanwhile, in this specification, equivalent weight (eq) refers to molar equivalent (eq / mol) relative to the method for preparing the metallocene compound or the catalyst composition for preparing the polypropylene resin according to one embodiment of the present invention.

[0088] In the catalyst composition for preparing the polypropylene resin composition according to one embodiment of the present invention, the metallocene compound of Chemical Formula 1 can be used in the form of a supported catalyst (wherein the metallocene compound is supported on a carrier) or in the form of an unsupported catalyst. In particular, in terms of ensuring the stability of the polymerization process using the catalyst composition and uniform control of physical properties, the metallocene compound is more preferably used in the form of a supported catalyst.

[0089] As the carrier, a carrier containing highly reactive hydroxyl groups or siloxane groups on its surface can be used. Preferably, a carrier containing highly reactive hydroxyl groups and siloxane groups that has been dried at a high temperature to remove moisture on the surface can be used.

[0090] For example, silica, silica-alumina, silica-magnesia, etc. dried at high temperature can be used, and it can generally include oxide, carbonate, sulfate and nitrate components, such as Na2O, K2CO3, BaSO4 and Mg(NO3)2, etc.

[0091] The drying temperature of the carrier is preferably from about 200°C to about 800°C, more preferably from about 300°C to about 600°C, and most preferably from about 300°C to about 400°C. When the drying temperature of the carrier is below about 200°C, excessive moisture remains, and the moisture on the surface may react with the co-catalyst. When the drying temperature is above about 800°C, the pores on the carrier surface may merge with each other, reducing the surface area, and many hydroxyl groups may be lost from the surface, leaving only siloxane groups. As a result, the number of reaction sites with the co-catalyst may decrease, which is not preferred.

[0092] For example, the amount of hydroxyl groups on the support surface is preferably from about 0.1 mmol / g to about 10 mmol / g, more preferably from about 0.5 mmol / g to about 5 mmol / g. The amount of hydroxyl groups on the support surface can be controlled by the preparation method and preparation conditions or drying conditions of the support, such as temperature, time, vacuum degree or spray drying. When the amount of hydroxyl groups is less than about 0.1 mmol / g, the reaction sites with the co-catalyst may be reduced. When the amount of hydroxyl groups is greater than about 10 mmol / g, in addition to the hydroxyl groups present on the surface of the support particles, it may be caused by moisture, which is not preferred.

[0093] When the metallocene compound of Chemical Formula 1 is supported on a support, the weight ratio of the total transition metal contained in the metallocene compound represented by Chemical Formula 1 to the support may be from about 1:1 to about 1:1000. When the support and the metallocene compound are included in the above weight ratio, appropriate activity of the supported catalyst may be exhibited, which may be advantageous in terms of maintaining catalytic activity and economic feasibility. More specifically, the weight ratio of the compound of Chemical Formula 1 to the support may be from 1:10 to 1:30, more specifically from 1:15 to 1:20.

[0094] In addition to the metallocene compound of Chemical Formula 1 and the support, the catalyst composition may further include a co-catalyst in terms of high activity and improved process stability.

[0095] Specifically, the co-catalyst may include one or more compounds represented by Formula 2:

[0096] [Chemical Formula 2]

[0097] -[Al(R 21 )-O] m -

[0098] In Chemical Formula 2,

[0099] R 21 are the same as or different from each other and are each independently halogen, C 1-20 Alkyl or C 1-20 haloalkyl; and

[0100] m is an integer greater than or equal to 2.

[0101] Examples of the compound represented by Chemical Formula 2 may include aluminoxane type compounds such as methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, butylaluminoxane, and the like, and any one thereof or a mixture of two or more thereof may be used.

[0102] In addition, the co-catalyst may include one or more of the compounds represented by Chemical Formula 3:

[0103] [Chemical Formula 3]

[0104] J(R 31 )3

[0105] In Chemical Formula 3,

[0106] R 31 are the same as or different from each other and are each independently halogen, C 1-20 Alkyl or C 1-20 haloalkyl; and

[0107] J is aluminum or boron.

[0108] Examples of the compound represented by Chemical Formula 3 may include trimethylaluminum, triethylaluminum, triisobutylaluminum, tripropylaluminum, tributylaluminum, dimethylaluminum chloride, triisopropylaluminum, tri-sec-butylaluminum, tricyclopentylaluminum, tripentylaluminum, triisopentylaluminum, trihexylaluminum, trioctylaluminum, ethyldimethylaluminum, methyldiethylaluminum, triphenylaluminum, tri-p-tolylaluminum, dimethylaluminum methoxide, dimethylaluminum ethoxide, trimethylboron, triethylboron, triisobutylboron, tripropylboron, tributylboron, and the like, and more specifically selected from trimethylaluminum, triethylaluminum, and triisobutylaluminum.

[0109] In addition, the co-catalyst may include one or more of the compounds represented by Chemical Formula 4:

[0110] [Chemical Formula 4]

[0111] [EH] + [ZQ4] -

[0112] In Chemical Formula 4,

[0113] E is a neutral or cationic Lewis base;

[0114] H is a hydrogen atom;

[0115] Z is a Group 13 element; and

[0116] Q are the same or different from each other and are each independently C 6-20 Aryl or C 1-20 Alkyl, where C 6-20 Aryl or C 1-20 The alkyl group is unsubstituted or substituted with one or more substituents selected from the group consisting of halogen, C 1-20 Alkyl, C 1-20 Alkoxy and C 6-20 A group consisting of aryloxy groups.

[0117] Specifically, in Chemical Formula 4, E may be an amine including one or more nitrogen atoms, wherein the amine may be substituted with C 6-20 Aryl or C 1-20 For example, E can be an amine including one or two nitrogen atoms, wherein the amine group can replace two or more C 6-20 Aryl or C 1-20 Alkyl or amine substituted with two or three C 6-18 Aryl or C 6-12 Aryl or C 1-12 Alkyl or C 1-6 alkyl.

[0118] For example, in Chemical Formula 4, [EH] + It may be a Bronsted acid.

[0119] Specifically, in Chemical Formula 4, Z may be aluminum or boron.

[0120] Specifically, in Chemical Formula 4, Q can be each substituted with C 6-18 Aryl or C 6-12 Aryl, or C 1-12 Alkyl or C 1-6 The alkyl group may have no substituents, as described above.

[0121] Examples of the compound represented by Chemical Formula 4 may 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 tetra(pentafluorophenyl)boron, N,N-diethylanilinium tetraphenylboron, N,N-diethylanilinium tetra(pentafluorophenyl)boron, diethylammonium tetra(pentafluorophenyl)boron, 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 tetra(pentafluorophenyl)aluminum, N,N-diethylanilinium tetraphenylaluminum, N,N-diethylanilinium tetra(pentafluorophenyl)aluminum, diethylammonium tetra(pentafluorophenyl)aluminum, triphenylphosphonium tetraphenylaluminum, trimethylphosphonium tetraphenylaluminum, tripropylammonium tetra(p-tolyl)boron, triethylammonium tetra(o, p-dimethylphenyl)boron, tributylammonium tetra(p-trifluoromethylphenyl)boron, triphenylcarbonium tetra(p-trifluoromethylphenyl)boron or triphenylcarbonium tetra(pentafluorophenyl)boron, etc., any one of which or a mixture of two or more thereof can be used.

[0122] When a co-catalyst is further included, the weight ratio of the metallocene compound of Chemical Formula 1 to the co-catalyst may be from about 1:1 to about 1:20. When the co-catalyst and the metallocene compound are included in the above weight ratio, appropriate activity of the supported catalyst may be exhibited, which may be advantageous in terms of maintaining catalytic activity and economic feasibility. More specifically, the weight ratio of the compound of Chemical Formula 1 to the co-catalyst may be from about 1:5 to about 1:20, or from about 1:5 to about 1:15.

[0123] Based on the weight of the support, for example, about 1 g of silica, the co-catalyst can be loaded in an amount of about 3 mmol or more, or about 5 mmol or more, and about 20 mmol or less, or about 15 mmol or less. When included within the above content range, the effect of improving catalytic activity by using the co-catalyst can be exhibited.

[0124] When the catalyst composition includes both the support and the co-catalyst, the catalyst composition can be prepared by a preparation method comprising the steps of supporting the co-catalyst compound on the support and supporting the compound represented by Chemical Formula 1 on the support. In this regard, the order of supporting the co-catalyst and the metallocene compound of Chemical Formula 1 may be changed as needed.

[0125] In this regard, as a reaction solvent for preparing the catalyst composition, a hydrocarbon solvent such as pentane, hexane, heptane, or the like, or an aromatic solvent such as benzene, toluene, or the like can be used.

[0126] Meanwhile, the polypropylene resin composition according to one embodiment of the present invention may be prepared by a method including polymerizing propylene monomers in the presence of a catalyst composition including one or more metallocene compounds represented by Chemical Formula 1 to prepare a polypropylene resin.

[0127] For example, propylene polymerization can be carried out using a single continuous slurry polymerization reactor, a loop slurry reactor, a gas phase reactor, or a solution reactor.

[0128] In particular, the polypropylene resin composition according to one embodiment of the present invention may be prepared by a step including homopolymerizing propylene in the presence of one or more metallocene compounds represented by Chemical Formula 1.

[0129] For example, the polypropylene resin composition according to one embodiment of the present invention may be prepared by a bulk slurry method in the presence of a catalyst composition including one or more metallocene compounds represented by Chemical Formula 1.

[0130] In this respect, the polymerization process can be carried out in a loop reactor and, for example, in a spheroidization process reactor comprising two loop reactors.

[0131] Specifically, the polymerization process consists of a reaction system comprising a plurality of loop reactors.Propylene homopolymer can be prepared by continuously polymerizing liquid propylene monomer in the presence of a catalyst and hydrogen in the reaction system comprising a plurality of loop reactors.

[0132] The preparation of the polypropylene resin may be carried out by a polymerization process in which propylene monomer is contacted in the presence of hydrogen in the presence of the above-mentioned catalyst composition.

[0133] Hydrogen activates the inert sites of the metallocene catalyst and causes chain transfer reactions, thereby controlling the molecular weight. The metallocene compound of the present invention has excellent hydrogen reactivity. Therefore, by controlling the amount of hydrogen used in the polymerization process, polypropylene with a desired molecular weight and melt index can be effectively obtained.

[0134] Based on the total mole number of propylene monomer, the amount of hydrogen introduced can be 10ppm to 360ppm. Since polymerization is carried out while introducing hydrogen in the above amount, a polypropylene resin with an optimal weight-average molecular weight range and the above-mentioned physical property requirements, particularly a narrow molecular weight distribution and a low melt index, can be prepared. When the input amount of hydrogen is less than 10ppm, the melt index of the prepared polypropylene resin is significantly reduced, resulting in poor fluidity and low discharge performance of the final polypropylene resin composition, making it impossible to carry out the spinning process. On the contrary, when the input amount of hydrogen exceeds 360ppm, the melt index of the polypropylene resin may become too high, and the fiber stiffness of the final polypropylene resin composition may be reduced. More specifically, based on the total mole number of propylene monomer, the amount of hydrogen introduced can be more than 30ppm, or more than 40ppm, or more than 50ppm, and less than 300ppm, or less than 250ppm, or less than 230ppm.

[0135] The polymerization process can be carried out by a continuous polymerization process, and for example, various polymerization processes known as olefin monomer polymerization processes can be employed, such as a continuous solution polymerization process, a bulk polymerization process, a suspension polymerization process, a slurry polymerization process, or an emulsion polymerization process. Furthermore, the polymerization reaction can be carried out by homopolymerizing propylene monomer using one or two continuous slurry polymerization reactors, a loop slurry reactor, a gas phase reactor, or a solution reactor. In particular, a continuous bulk-slurry polymerization process may be preferred in terms of obtaining a uniform molecular weight distribution and commercial production of the product.

[0136] Furthermore, the polymerization temperature may be 25° C. to 200° C., preferably 40° C. to 150° C., and more preferably 60° C. to 100° C. Furthermore, the polymerization pressure may be 1 kgf / cm 2 Up to 100kgf / cm 2 , preferably 1kgf / cm 2 Up to 80kgf / cm 2 , more preferably 5kgf / cm 2 Up to 50kgf / cm 2 The polymerization is carried out at such temperatures and pressures that homopolypropylene having the desired physical properties is produced in high yield.

[0137] In addition, the polymerization process may be performed by optionally further introducing one or more aluminum-based compounds represented by the following Chemical Formula 5 when polymerizing propylene monomer in the presence of a catalyst composition including one or more metallocene compounds represented by Chemical Formula 1 and hydrogen.

[0138] [Chemical Formula 5]

[0139] Al(R 51 )3

[0140] In Chemical Formula 5,

[0141] R 51 are the same as or different from each other and are each independently halogen, C 1-20 Alkyl or C 1-20 Halogenated alkyl.

[0142] Specifically, examples of the aluminum-based compound represented by Chemical Formula 5 include trimethylaluminum, triethylaluminum, triisobutylaluminum, tripropylaluminum, tributylaluminum, dimethylaluminum chloride, triisopropylaluminum, tri-sec-butylaluminum, tricyclopentylaluminum, tripentylaluminum, triisopentylaluminum, trihexylaluminum, trioctylaluminum, ethyldimethylaluminum, methyldiethylaluminum, triphenylaluminum, tri-p-tolylaluminum, dimethylaluminum methoxide, and dimethylaluminum ethoxide, and more specifically, one or more or two or more selected from trimethylaluminum, triethylaluminum, and triisobutylaluminum.

[0143] In addition, when the aluminum-based compound represented by Chemical Formula 5 is further introduced during the polymerization process, the amount of the aluminum-based compound may be 0.001% by weight or more and 1.2% by weight or less based on the total weight of the propylene monomer. Specifically, the amount of the aluminum-based compound represented by Chemical Formula 5 may be 0.01% by weight or more, or 0.02% by weight or more, or 0.05% by weight or more, or 0.08% by weight or more, or 0.1% by weight or more, and 1% by weight or less, or 0.8% by weight or less, or 0.5% by weight or less.

[0144] In particular, during the process of preparing polypropylene resin by polymerizing propylene monomer, when moisture or impurities are present in the polymerization reactor, a portion of the catalyst decomposes. Therefore, since the aluminum-based compound represented by Chemical Formula 5 acts as a scavenger that initially captures moisture or impurities present in the reactor, the activity of the catalyst used in the preparation can be maximized, and thus, a polyethylene resin that meets the above-mentioned physical property requirements can be more efficiently prepared. When this aluminum-based compound is not used, moisture or impurities act as catalyst poisons during the polymerization process, and thus the structural characteristics of the catalyst may change, such as reducing activity, and thus the required physical properties may not be met.

[0145] Meanwhile, in the present invention, after preparing the polypropylene resin by the method as described above, the molecular weight modifier described below is mixed under optimized conditions and melt extruded, thereby preparing a polypropylene resin composition, which has high stiffness and excellent process stability and processability compared to existing polypropylene using a Ziegler-Natta catalyst or polypropylene resin using a conventional metallocene catalyst (i.e., homopolypropylene or propylene copolymer, etc.), and at the same time has characteristics suitable for ultra-low basis weight, high stiffness non-woven fabrics, which can reduce the use of plastics in diapers, etc. in response to recent environmental issues.

[0146] Meanwhile, the polypropylene resin may have a molecular weight distribution as well as a melt index, a melting point, and a crystallization temperature within optimal ranges.

[0147] For example, the molecular weight distribution (Mw / Mn, MWD) of the polypropylene resin may be 2.0 or more and 3.0 or less. Specifically, the molecular weight distribution (Mw / Mn, MWD) of the polypropylene resin may be 2.1 or more, or 2.15 or more, or 2.2 or more, or 2.25 or more, or 2.3 or more, or 2.35 or more, or 2.38 or more, or 2.4 or more, or 2.45 or more, and 2.95 or less, or 2.9 or less, or 2.85 or less, or 2.8 or less, or 2.75 or less, or 2.7 or less, or 2.65 or less, or 2.6 or less.

[0148] In addition, the polypropylene resin can have a high weight average molecular weight while having an optimized molecular weight distribution. Specifically, the weight average molecular weight of the polypropylene resin can be more than 210,000 g / mol, or 210,000 g / mol to 375,000 g / mol. More specifically, the weight average molecular weight of the polypropylene resin can be more than 220,000 g / mol, or more than 230,000 g / mol, or more than 240,000 g / mol, or more than 250,000 g / mol, and less than 370,000 g / mol, or less than 360,000 g / mol, or less than 355,000 g / mol, or less than 350,000 g / mol.

[0149] According to another embodiment of the present invention, the molecular weight distribution, weight average molecular weight (Mw), and number average molecular weight (Mn) of the polypropylene resin may be measured using a gel permeation chromatography (GPC) apparatus, and the detailed measuring method is as described above.

[0150] In addition, the melt index of the polypropylene resin (MI measured at 230° C. under a load of 2.16 kg) is as measured at 230° C. under a load of 2.16 kg according to the American Society for Testing and Materials standard ASTM D 1238. 2.16 ) can be from 2 g / 10 min to 11 g / 10 min. Specifically, the melt index (MI) of the polypropylene resin is 2.16) may be 2.2 g / 10 min or more, or 2.5 g / 10 min or more, or 2.8 g / 10 min or more, or 3 g / 10 min or more, or 3.2 g / 10 min or more, or 3.5 g / 10 min or more, or 3.8 g / 10 min or more, or 4 g / 10 min or more, or 4.3 g / 10 min or more, or 4.5 g / 10 min or more, or 4.8 g / 10 min or more, or 5 g / 10 min or more, and 10.5 g / 10 min or less, or 10 g / 10 min or less, or 9.8 g / 10 min or less, or 9.5 g / 10 min or less, or 9.2 g / 10 min or less, or 9 g / 10 min or less, or 8.8 g / 10 min or less, or 8.5 g / 10 min or less, or 8.2 g / 10 min or less, or 8 g / 10 min or less, or 7.8 g / 10 min or less.

[0151] Meanwhile, the polypropylene resin may have optimized melting point (Tm) and crystallization temperature (Tc), as well as molecular weight distribution, weight average molecular weight, and melt index.

[0152] For example, the polypropylene resin may have a melting point (Tm) of 135°C or higher, or 135°C to 155°C, and a crystallization temperature (Tc) of 115°C or lower, or 95°C to 115°C or lower.

[0153] Specifically, the melting point (Tm) of the polypropylene resin may be 136° C. or higher, or 138° C. or higher, or 140° C. or higher, or 142° C. or higher, or 145° C. or higher, or 148° C. or higher, or 150° C. or higher, and 154.5° C. or lower, or 154° C. or lower, or 153.5° C. or lower, or 153° C. or lower, or 152.5° C. or lower, or 152° C. or lower. In particular, the melting point (Tm) of the polypropylene resin may be 135° C. or higher in terms of ensuring excellent mechanical properties (such as high tenacity) and excellent heat resistance during fiber production.

[0154] In addition, the crystallization temperature (Tc) of the polypropylene resin may be 113.5° C. or less, or 113° C. or less, or 112.5° C. or less, or 112° C. or less, or 111.5° C. or less, or 111° C. or less, or 111.5° C. or less, or 110° C. or less, and 96° C. or more, or 98° C. or more, or 100° C. or more, or 102° C. or more, or 105° C. or more. In particular, the crystallization temperature (Tc) of the polypropylene resin may be 115° C. or less in terms of preventing a rapid increase in viscosity and spinning defects due to excessive solidification of spun filaments during fiber production.

[0155] According to another embodiment of the present invention, the melting point (Tm) and crystallization temperature (Tc) of the polypropylene resin may be measured using a differential scanning calorimeter (DSC, for example, device name: DSC2920, manufacturer: TA Instruments), and the detailed measuring method is as described above.

[0156] Subsequently, the method for preparing a polypropylene resin composition according to one embodiment of the present invention includes the step of melt-extruding a mixture comprising the polypropylene resin prepared by the above polymerization method and a molecular weight modifier at 120° C. to 300° C. both inclusive.

[0157] In particular, polypropylene resin can be mixed with a molecular weight modifier and then extruded and pelletized.

[0158] The molecular weight modifier may be a linear acyclic organic peroxide compound.

[0159] Specifically, the molecular weight modifier may be an acyclic organic peroxide compound having 4 to 32 carbon atoms, or 6 to 24 carbon atoms, or 8 to 16 carbon atoms.

[0160] For example, the molecular weight modifier may be one or more selected from the group consisting of 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (DHBP), 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexyne (DYBP), and di-tert-butyl peroxide (DTBP).

[0161] In addition, the extrusion and pelletizing process of the mixture including the polypropylene resin and the molecular weight modifier may be performed according to a common extrusion method and using a twin-screw extruder, wherein the temperature for melting the mixed composition is controlled within a range of 120° C. to 300° C. both inclusive.

[0162] In addition, when the pressure is further controlled together with the mold temperature, the mold pressure can be 20 bar or more, or 30 bar or more, 50 bar or less, or 35 bar or less. When the pressure is controlled within this range, the shape and physical properties of the polypropylene resin composition can be easily achieved.

[0163] Simultaneously, the mixture comprising the polypropylene resin and the molecular weight modifier may also comprise one or more additives, such as antioxidants, lubricants, UV stabilizers, neutralizers, dispersants, weathering agents, antistatic agents, UV stabilizers, slip agents, antiblocking agents, talcum, nucleating agents etc. More specifically, as additives, the mixture may also comprise one or more selected from the group consisting of antioxidants, lubricants, UV stabilizers and neutralizers. These additives may be used without restriction, as long as they are known to be applicable to the preparation of the polypropylene resin composition, and therefore a detailed description of the type and amount of the above-mentioned additives has been omitted.

[0164] However, when preparing polypropylene resin, the best combination of physical properties of the polypropylene resin can be achieved by controlling the catalyst and polymerization conditions.

[0165] The polypropylene resin composition according to one embodiment of the present invention prepared by the above-mentioned preparation method has an optimized melt index and a narrow molecular weight distribution, which enables the production of fibers with thin thickness and high tenacity. It can be particularly used to manufacture spunbonded nonwoven fabrics with high tenacity and ultra-low basis weight characteristics to minimize weight when used in diapers, etc.

[0166] Polypropylene fiber and spunbond nonwoven fabric

[0167] According to yet another embodiment of the present invention, there are provided polypropylene fibers and spunbonded nonwoven fabrics, each comprising the polypropylene resin composition.

[0168] For example, the polypropylene fibers of the present invention may have a tenacity of 6.95 gf / denier or greater as measured according to ASTM D 638.

[0169] Furthermore, the spunbonded nonwoven fabric of the present invention may be composed of fibers comprising the above-mentioned polypropylene resin composition.

[0170] The polypropylene fiber of the present invention and the spunbonded nonwoven fabric produced using the same can be produced according to a conventional method except for using the above-mentioned polypropylene resin composition.

[0171] Hereinafter, preferred exemplary embodiments will be provided to better understand the present invention. However, the following exemplary embodiments are provided only to more easily understand the present invention, but the content of the present invention is not limited thereto.

[0172] [Example]

[0173] <Preparation of Metallocene Catalyst>

[0174] Catalyst Preparation Example 1

[0175]

[0176] Step 1) Preparation of (6-tert-butoxyhexyl)dichloromethylsilane

[0177] At -100°C, 100 mL of tert-butoxyhexylmagnesium chloride solution (about 0.14 mol, ether) was slowly added dropwise to 100 mL of trichloromethylsilane solution (about 0.21 mol, hexane) over 3 hours, followed by stirring at room temperature for 3 hours.

[0178] The transparent organic layer was separated from the mixed solution, and then the separated transparent organic layer was dried under vacuum to remove excess trichloromethylsilane. As a result, transparent liquid (6-tert-butoxyhexyl)dichloromethylsilane was obtained (yield 84%).

[0179] 1 H NMR (500MHz, CDCl3, 7.24ppm): 0.76(3H,s), 1.11(2H,t), 1.18(9H,s), 1.32~1.55(8H,m), 3.33(2H,t).

[0180] Step 2 Preparation of (6-tert-butoxyhexyl)(methyl)-bis(2-methyl-4-phenylindenyl)silane

[0181] At 0 ° C, 15.4 mL of n-butyl lithium solution (2.5 M, hexane solvent) was slowly added dropwise to 77 mL of 2-methyl-4-phenylindene toluene / THF = 10 / 1 solution (34.9 mmol), and stirred at 80 ° C for 1 hour, and then stirred at room temperature for 1 day. Thereafter, 5 g of (6-tert-butoxyhexyl)dichloromethylsilane prepared in step 1) was slowly added dropwise to the mixed solution at -78 ° C, stirred for about 10 minutes, and then stirred at 80 ° C for 1 hour. Then, water was added to separate the organic layer, purified using a silica column, and dried under vacuum to obtain a viscous yellow oil with a yield of 78% (racemic: meso = 1:1).

[0182] 1 H NMR(500MHz, CDCl3,7.24ppm):0.10(3H,s),0.98(2H,t),1.25(9H,s),1.36~1.50(8H,m),1.62(8H,m),2.26(6 H,s),3.34(2H,t),3.81(2H,s),6.87(2H,s),7.25(2H,t),7.35(2H,t),7.45(4H,d),7.53(4H,t),7.61(4H,d).

[0183] Step 3) Preparation of [(6-tert-butoxyhexylmethylsilane-diyl)-bis(2-methyl-4-phenylindenyl)]zirconium dichloride

[0184] A solution of n-butyllithium (2.5 M in hexane) was slowly added dropwise to 50 mL of a 1 / 1 ether / hexane solution (3.37 mmol) of (6-tert-butoxyhexyl)(methyl)bis(2-methyl-4-phenylindenyl)silane prepared in Step 2 at -78°C, stirred at room temperature for approximately 2 hours, and then dried under vacuum. The salt was then washed with hexane, filtered, and dried under vacuum to obtain a yellow solid. The ligand salt synthesized in the glove box and bis(N,N'-diphenyl-1,3-propanediamino)zirconium dichloride bis(tetrahydrofuran) [Zr(C5H6NCH2CH2CH2NC5H6)Cl2(C4H8O)2] were weighed in a Schlenk flask, and ether was slowly added dropwise at -78°C, followed by stirring at room temperature for one day. The red reaction solution was then isolated by filtration, and 4 equivalents of ethereal HCl (1 M) were slowly added dropwise at -78°C, followed by stirring at room temperature for 3 hours. Then, the solution was filtered and dried under vacuum to obtain an orange solid bridged metallocene compound with a yield of 85% (rac:meso=10:1).

[0185] 1 H NMR(500MHz,C6D6,7.24ppm):1.19(9H,s),1.32(3H,s),1.48~1.86(10H,m),2.25(6H,s),3 .37(2H,t),6.95(2H,s),7.13(2H,t),7.36(2H,d),7.43(6H,t),7.62(4H,d),7.67(2H,d).

[0186] Step 4) Preparation of supported catalyst

[0187] 3 g of silica was weighed in advance in a Shrink flask, 52 mmol of methylaluminoxane (MAO) was added and reacted at 90 ° C for 24 hours. After precipitation, the upper layer was removed and then washed twice with toluene. 240 μmol of the bridged metallocene compound synthesized in step 3) above dissolved in toluene was added thereto and reacted at 40 ° C for 5 hours. After the reaction was completed and the precipitation was completed, the upper solution was removed, and the remaining reaction product was washed with toluene, washed again with hexane, and vacuum dried to obtain 5 g of silica-supported metallocene catalyst in the form of solid particles.

[0188] Catalyst Preparation Example 2

[0189]

[0190] Step 1 Preparation of (diethylsilane-diyl)-bis((2-methyl-4-tert-butyl-phenylindenyl)silane

[0191] 2-Methyl-4-tert-butyl-phenylindene (20.0 g) was dissolved in a mixed solvent of toluene and tetrahydrofuran (volume ratio of toluene / THF = 10 / 1, 220 mL), and then an n-butyllithium solution (2.5 M, hexane solvent, 22.2 g) was slowly added dropwise at 0° C., followed by stirring at room temperature for 1 day. Thereafter, diethyldichlorosilane (6.2 g) was slowly added dropwise to the mixed solution at −78° C., stirred for about 10 minutes, and then stirred at room temperature for one day. Thereafter, water was added to separate the organic layer, and the solvent was distilled under reduced pressure to obtain (diethylsilane-diyl)-bis((2-methyl-4-tert-butyl-phenylindene)silane.

[0192] Step 2) Preparation of [(diethylsilane-diyl)-bis((2-methyl-4-tert-butyl-phenylindenyl)]zirconium dichloride

[0193] The (diethylsilane-diyl)-bis((2-methyl-4-tert-butyl-phenylindenyl)silane prepared in step 1 was dissolved in a mixed solvent (120 mL) of toluene / THF in a volume ratio of 5 / 1, and n-butyllithium solution (2.5 M, hexane solvent, 22.2 g) was slowly added dropwise at -78°C, and stirred at room temperature for one day. Zirconium chloride (8.9 g) was diluted in toluene (20 mL) in the reaction solution, slowly added dropwise at -78°C, and stirred at room temperature for one day. The solvent in the reaction solution was removed under reduced pressure, dichloromethane was added and filtered, and the filtrate was distilled under reduced pressure. Recrystallization was carried out using toluene and hexane to obtain high-purity racemic-[(diethylsilane-diyl)-bis((2-methyl-4-tert-butyl-phenylindenyl)]zirconium dichloride (10.1 g, yield: 34%, racemic:meso molar ratio = 20:1).

[0194] Step 3) Preparation of supported catalyst

[0195] 100g silica and 10% by weight methylaluminoxane (670g) are put into 3L reactor and reacted at 90 ℃ for 24 hours.After precipitation, remove the upper layer, then wash twice with toluene. The bridged metallocene compound racemization-[(diethylsilane-two bases)-bis((2-methyl-4-tert-butyl-phenyl indenyl)] zirconium dichloride (5.8g) prepared in step 2 is diluted with toluene and put into this reactor, and reacted at 70 ℃ for 5 hours.After reaction and precipitation are completed, remove the upper solution, remaining reaction product is washed with toluene, then washed with hexane again, vacuum dried, to obtain the silica-supported metallocene catalyst of 150g solid particle form.

[0196] Comparative Catalyst Preparation Example 1

[0197]

[0198] Step 1) Preparation of the ligand compound (2-methyl-4-(3',5'-di-tert-butylpropyl)indacenyl)dimethyl(2,3,4,5-tetramethylcyclopentadienyl)silane

[0199] 2,3,4,5-tetramethylcyclopentadiene (TMCP) was dissolved in tetrahydrofuran (THF), and n-butyllithium (n-BuLi, 1.05eq) was slowly added dropwise at -25°C and stirred at room temperature for 3 hours. Thereafter, dichlorodimethylsilane (1.05eq) was introduced at -10°C and stirred at room temperature overnight. In another reactor, 2-methyl-4-(3',5'-di-tert-butylphenyl) indacene (1eq) was dissolved in a mixed solvent of toluene / tetrahydrofuran (toluene / THF) (volume ratio of 3 / 2, 0.5M), and n-BuLi (1.05eq) was slowly added dropwise at -25°C, and stirred at room temperature for 3 hours. Thereafter, CuCN (2mol%) was introduced, stirred for 30 minutes, and the first reactant single Si solution was introduced. Thereafter, the solution was stirred at room temperature overnight, treated with water, and then dried to obtain a ligand.

[0200]

[0201] Step 2) Preparation of transition metal compound dimethylsilanediyl(2-methyl-4-(3',5'-di-tert-butylphenyl)indacene)(2,3,4,5-tetramethylcyclopentadienyl)zirconium dichloride

[0202] The ligand prepared above is dissolved in toluene / ether (volume ratio is 2 / 1,0.53M), n-BuLi (2.05eq) is introduced at-25 ℃, and stirred at room temperature for 5 hours. By in a separate flask, ZrCl (1eq) is mixed with toluene (0.17M) to prepare slurry, introduced into the ligand solution, and stirred at room temperature overnight. When the reaction is complete, the solvent is dried under vacuum, methylene chloride is reintroduced to remove LiCl by a filter etc., the filtrate is dried under vacuum, and methylene chloride / hexane is added to recrystallize at room temperature. After this, the gained solid is filtered and vacuum dried to obtain the title metallocene compound.

[0203] The NMR data of the transition metal compound thus obtained were measured using a Bruker AVANCE III HD 500 MHz NMR / PABBO (1H / 19F / Broad band) probe: 1H, solvent: CDCl3.

[0204] 1H-NMR(500MHz, CDCl3):7.73(s,2H),7.56(s,1H),7.42(s,1H),6.36(s,1H),2.85- 2.80(m,4H),2.12(s,6H),1.95(m,2H),1.79(s,9H),1.31(s,18H),1.00(s,6H)ppm.

[0205] Step 3) Preparation of supported catalyst

[0206] 100g of silica and 10% by weight of methylaluminoxane (670g) are placed in a 3L reactor and reacted at 90°C for 24 hours. After precipitation, the upper layer is removed and washed twice with toluene. The transition metal compound dimethylsilanediyl (2-methyl-4-(3', 5'-di-tert-butylphenyl) indoxane) (2,3,4,5-tetramethylcyclopentadienyl) zirconium dichloride (5.8g) prepared in step 2 is diluted with toluene, placed in a reactor, and reacted at 70°C for 5 hours. After the reaction and precipitation are completed, the upper solution is removed, and the remaining reaction product is washed with toluene, then washed again with hexane, and vacuum dried to obtain 150g of silica-supported metallocene catalysts in the form of solid particles.

[0207] <Preparation of Homopolypropylene>

[0208] Preparation Example 1

[0209] In the presence of the silica-supported metallocene catalyst prepared according to Catalyst Preparation Example 1, bulk-slurry polymerization of propylene was carried out using two consecutive loop reactors.

[0210] Specifically, triethylaluminum (TEAL) and hydrogen are introduced separately using a pump, and the silica-supported metallocene catalyst is used in the form of a slurry catalyst. The silica-supported metallocene catalyst is mixed with oil and grease to prepare a 20% by weight mixture (in the form of a slurry catalyst). Here, the input amount of triethylaluminum (TEAL) is 50ppm, which is a weight value (ppm) based on the total weight of the monomers used to form homopolypropylene; the input amount of hydrogen is 140ppm, which is a molar ratio value (ppm) based on the total molar number of the monomers used to form homopolypropylene. In addition, the reactor is operated at a temperature of 70°C and a production rate of about 40kg / h / hour. At this time, the polymerization pressure is maintained at 35kg / cm 2 , propylene is introduced at 40 kg / h.

[0211] The measurement results of physical properties of the homopolypropylene of Preparation Example 1 obtained by the above-mentioned bulk-slurry polymerization method of propylene are shown in Table 1 below.

[0212] Preparation Example 2

[0213] Bulk-slurry polymerization of propylene was carried out in the same manner as in Preparation Example 1 except that the input amount of hydrogen was changed to 50 ppm, thereby producing homopolypropylene of Preparation Example 2.

[0214] Preparation Example 3

[0215] Bulk-slurry polymerization of propylene was carried out in the same manner as in Preparation Example 1, except that the hydrogen input was changed to 230 ppm in the presence of the silica-supported metallocene catalyst prepared according to Catalyst Preparation Example 2, to thereby prepare homopolypropylene of Preparation Example 3.

[0216] Preparation Example 4

[0217] Bulk-slurry polymerization of propylene was carried out in the same manner as in Preparation Example 3 except that the input amount of hydrogen was changed to 100 ppm, thereby producing homopolypropylene of Preparation Example 4.

[0218] Comparative Preparation Example 1

[0219] Bulk-slurry polymerization of propylene was carried out in the same manner as in Preparation Example 1 except that the input amount of hydrogen was changed to 260 ppm, thereby preparing homopolypropylene of Comparative Preparation Example 1.

[0220] Comparative Preparation Example 2

[0221] Bulk-slurry polymerization of propylene was carried out in the same manner as in Preparation Example 3 while changing the input amount of hydrogen to 50 ppm, thereby preparing homopolypropylene of Comparative Preparation Example 2.

[0222] Comparative Preparation Example 3

[0223] The commercially available H5300 TM Homopolypropylene prepared as Comparative Preparation Example 3 (manufactured by LG Chem. Co., Ltd.) was a homopolypropylene prepared using a Ziegler-Natta catalyst (Z / N).

[0224] Comparative Preparation Example 4

[0225] Bulk-slurry polymerization of propylene was carried out in the same manner as in Comparative Preparation Example 1 except that the input amount of hydrogen was changed to 380 ppm, thereby preparing homopolypropylene of Comparative Preparation Example 4.

[0226] Comparative Preparation Example 5

[0227] Bulk-slurry polymerization of propylene was carried out in the same manner as in Preparation Example 1, except that the polymerization process was carried out in the presence of the silica-supported metallocene catalyst prepared according to Comparative Catalyst Preparation Example 1, and the input amount of hydrogen was changed to 400 ppm, thereby preparing homopolypropylene of Comparative Preparation Example 5.

[0228] <Experimental Example 1: Evaluation of Physical Properties of Homopolypropylene>

[0229] The physical properties of the homopolypropylenes of Preparation Examples 1 to 4 and Comparative Preparation Examples 1 to 5 were evaluated by the following methods, and the measurement results are shown in Table 1 below.

[0230] (1) Melt index

[0231] Melt index (MI) was measured at 230°C under a load of 2.16 kg according to ASTM D 1238. 2.16 ), and expressed as the weight (g) of the polymer melted out in 10 minutes.

[0232] (2) Weight average molecular weight (Mw) and molecular weight distribution (MWD, polydispersity index)

[0233] The weight average molecular weight (Mw) and number average molecular weight (Mn) of the homopolypropylenes according to the Preparation Examples and the Comparative Preparation Examples were measured using gel permeation chromatography (GPC, manufactured by Waters), and the weight average molecular weight was divided by the number average molecular weight to calculate the molecular weight distribution (MWD, Mw / Mn).

[0234] Specifically, use Waters PL-GPC220 instrument as gel permeation chromatography (GPC) instrument, and use Polymer Laboratories PLgel MIX-B 300mm length column.At this moment, measuring temperature is 160 ℃, and using 1,2,4-trichlorobenzene as solvent, flow rate is 1mL / min.Each polypropylene sample according to preparation example and comparative preparation example is dissolved in 1,2,4-trichlorobenzene containing 0.0125% BHT at 160 ℃ by using GPC analyzer (PL-GP220) for 10 hours to pre-treat, then with the amount of 200 μ L supply.Use the calibration curve formed with polystyrene standard sample to obtain the value of Mw and Mn. Nine polystyrene standard samples were used, whose molecular weights were 2000 g / mol, 10000 g / mol, 30000 g / mol, 70000 g / mol, 200000 g / mol, 700000 g / mol, 2000000 g / mol, 4000000 g / mol, and 100000000 g / mol, respectively.

[0235] (3) Melting point (Tm) and crystallization temperature (Tc)

[0236] Use differential scanning calorimeter (DSC, device name: DSC2920, manufacturer: TA instrument) to measure the melting point (Tm) and crystallization temperature (Tc) of the homopolypropylene according to preparation example and comparative preparation example. Specifically, homopolypropylene is heated to 200 ℃, and then kept at this temperature for 5 minutes. The temperature is reduced to 30 ℃, and then when the temperature is raised again, the temperature corresponding to the peak value of the DSC (differential scanning calorimeter, manufactured by TA) curve is determined as the melting point (Tm). Thereafter, when the temperature is reduced to 30 ℃ again, the peak of the curve is determined as the crystallization temperature (Tc). At this time, the heating and cooling rate is 10 ℃ / min, and the melting point (Tm) and crystallization temperature (Tc) are represented by the results measured in the second heating and cooling cycle.

[0237] Melt index (MI) of homopolypropylene of Preparation Examples 1-4 and Comparative Preparation Examples 1-5 2.16 ), weight average molecular weight (Mw), molecular weight distribution (MWD, Mw / Mn), melting point (Tm) and crystallization temperature (Tc) are shown in Table 1 below.

[0238] Table 1

[0239]

[0240] <Preparation of Polypropylene Resin Composition>

[0241] Example 1

[0242] The homopolypropylene of Preparation Example 1 and 500 ppm of phenolic antioxidant Irganox as an antioxidant were mixed. TM 1010 (manufactured by BASF) and 1000 ppm of the phosphorus antioxidant Irgafos TM 168 (manufactured by BASF) and 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (DHBP, (CH3)3COOC(CH3)2CH2-CH2(CH3)2COOC(CH3)3] as a molecular weight modifier were mixed in the amounts shown in Table 2 below. The thus obtained mixture was reacted and extruded using a 25 mm twin-screw extruder (manufactured by JSW) at temperatures of 230° C. (feeding section), 270° C. (mixing section) and 215° C. (compression section) with a residence time of 25 seconds at each stage for feeding, mixing and compression, thereby producing a masterbatch, which was then pelletized to prepare a pellet-type polypropylene resin composition (average diameter of the pellets: 4 mm). Meanwhile, the input amounts of the antioxidant and the molecular weight modifier are weight values ​​(ppm) based on the total weight of the homopolypropylene resin composition.

[0243] Examples 2 to 8

[0244] Pellet-type polypropylene resin compositions of Examples 2 to 8 were respectively prepared in the same manner as in Example 1, except that the type of homopolypropylene and the content of the molecular weight modifier were changed as shown in Table 2 below.

[0245] Comparative Examples 1 to 6

[0246] Pellet-type polypropylene resin compositions of Comparative Examples 1 to 6 were respectively prepared in the same manner as in Example 1, except that the type of homopolypropylene and the content of the molecular weight modifier were changed as shown in Table 2 below.

[0247] Comparative Example 7

[0248] Commercially available MR2001 TM (manufactured by Total) was used as a pellet-type polypropylene resin composition comprising homopolypropylene prepared using a metallocene catalyst (commercial product 1, MR2001 manufactured by Total).

[0249] Comparative Example 8

[0250] Commercially available MH7700S TM (manufactured by LG Chemical Co., Ltd.) was used as a pellet-type polypropylene resin composition comprising homopolypropylene prepared using a metallocene catalyst (commercial product 2, MH7700S manufactured by LG Chemical Co., Ltd.).

[0251] Comparative Example 9

[0252] A pellet-type polypropylene resin composition of Comparative Example 9 was prepared in the same manner as in Example 1, except that the homopolypropylene of Comparative Preparation Example 4 was used alone and no molecular weight modifier was used, as shown in Table 2 below.

[0253] Comparative Example 10

[0254] A pellet-type polypropylene resin composition of Comparative Example 10 was prepared in the same manner as in Example 1, except that the homopolypropylene of Comparative Preparation Example 5 was used alone and no molecular weight modifier was used, as shown in Table 2 below.

[0255] Comparative Example 11

[0256] The pellet-type polypropylene resin composition of Comparative Example 11 was prepared in the same manner as in Example 1, except that a propylene copolymer mixture including a propylene-ethylene random copolymer, a low-crystalline polypropylene resin, and a polyethylene-based resin was used instead of homopolypropylene as the polypropylene resin, and the content of the molecular weight modifier was changed to 400 ppm, as shown in Table 2 below.

[0257] Specifically, the propylene copolymer mixture includes 85 parts by weight of a propylene-ethylene random copolymer, 5 parts by weight of a low-crystalline polypropylene resin, and 10 parts by weight of a polyethylene resin, based on a total of 100 parts by weight of the mixture. Here, as the propylene-ethylene random copolymer, a product having an ethylene content of 5 mol%, a melt index (measured at 230° C. under a load of 2.16 kg) of 28 g / 10 min, and a molecular weight distribution (Mw / Mn) of 3.5 (manufactured by LOTTE Chemical) was used. As the low-crystalline polypropylene resin, a commercially available low-crystalline polypropylene resin prepared using a metallocene catalyst, having an [mmmm] value of 40% to 50%, a melt index (measured at 230° C. under a load of 2.16 kg) of 50 g / 10 min, and a molecular weight distribution (Mw / Mn) of 2.5 (manufactured by Idemitsu) was used. As the polyethylene resin, an ethylene / 1-butene copolymer having a 1-butene content of 3 mol%, a density of 0.960 g / cm 3 , a product having a melt index (measured at 190° C. under a load of 2.16 kg) of 18 g / 10 min and a molecular weight distribution (Mw / Mn) of 5.0 (manufactured by LOTTE Chemical).

[0258] <Experimental Example 2: Evaluation of Physical Properties of Polypropylene Resin Composition>

[0259] The melting point (Tm), crystallization temperature (Tc), melt index (MI) and the crystallization temperature (Tc) of the polypropylene resin compositions of Examples 1 to 8 and Comparative Examples 1 to 11 were measured in the same manner as in Experimental Example 1. 2.16 ), weight average molecular weight (Mw) and molecular weight distribution (MWD, Mw / Mn), and the results are shown in Table 2 below.

[0260] Table 2

[0261]

[0262] As shown in Table 2, the polypropylene resin compositions of Examples 1 to 8 achieved a molecular weight distribution (MWD, Mw / Mn) of 1.85 to 2.33, while the melt index (MI 2.16 ) is 25 g / 10 min to 34 g / 10 min, the melting point (Tm) is above 135 ° C, and the crystallization temperature (Tc) is below 115 ° C, which is within the optimal range.

[0263] In contrast, the polypropylene resin compositions of Comparative Examples 1 to 11 have a broad molecular weight distribution (MWD, Mw / Mn), or an excessively low or high melt index (MI 2.16), and unoptimized melting point (Tm) or crystallization temperature (Tc). In particular, Comparative Example 1 showed a broad molecular weight distribution (MWD, Mw / Mn) of 2.57 and a too low melt index (MI) of 16 g / 10 min. 2.16 By increasing the use of molecular weight modifier, Comparative Example 2 has a narrow molecular weight distribution (MWD, Mw / Mn) of 2.19, but it has a high melt index (MI) of 55 g / 10 min. 2.16 ) and a very low weight average molecular weight of 149,000 g / mol. The polypropylene resin compositions of Comparative Examples 3 to 9 showed melt indices (MI) of 25 g / 10 min and 34 g / 10 min. 2.16 ), but Comparative Example 4 showed an excessively narrow molecular weight distribution (MWD, Mw / Mn) of 1.6, and Comparative Examples 3 and 5 to 9 showed excessively broad molecular weight distributions (MWD, Mw / Mn) of 2.4 to 2.8. In particular, when preparing a polypropylene resin, Comparative Example 9 achieved a melt index of 25 g / 10 min, but maintained a broad molecular weight distribution (MWD, Mw / Mn) of 2.8 in the absence of a molecular weight modifier. In contrast, the polypropylene resin composition of Comparative Example 10 achieved a melt index of 25 g / 10 min and a molecular weight distribution (MWD, Mw / Mn) of 2.4 when preparing a polypropylene resin, but had an excessively high crystallization temperature (Tc) of 118°C. In addition, even with the use of a molecular weight modifier, Comparative Example 11 showed an excessively broad molecular weight distribution (MWD, Mw / Mn) of greater than 2.8 and a very low weight average molecular weight of less than 150,000 g / mol.

[0264] <Experimental Example 3: Production of Polypropylene Fiber and Evaluation of Physical Properties>

[0265] Fibers were produced using the polypropylene resin compositions of Examples and Comparative Examples, and the toughness and elongation of the produced fibers were evaluated.

[0266] Fiber manufacturing

[0267] The polypropylene resin compositions prepared in Examples and Comparative Examples were spun using a spinning-drawing type spinning machine.

[0268] Specifically, a polypropylene resin composition is introduced into a spinning machine, and the molten resin composition is discharged from a die as a fine thread, which is then cooled and solidified by a cooling air flow. The resulting undrawn yarn is stretched while passing through a first roller and a second roller, and a polypropylene fiber with a fineness of 2 deniers (DPF, denier / filament) is manufactured. For reference, denier is an international unit for indicating fiber thickness. 1 denier refers to a unit weight of 1g per 9000m standard length.

[0269] In addition, the spinning process was carried out using a nozzle diameter of 0.25pi / 24-filament die head, and during spinning, the speed of the gear pump was 19 rpm, the discharge amount of each hole was 2.5 g / min / hole, the spinning temperature (extrusion temperature) was 230°C, the tube temperature was 220°C, the die head temperature was 210°C, the cooling temperature (quenching air temperature) was about 20°C, the first roller temperature was 60°C, the roller speed was 1000 m / min, the second roller temperature was 120°C, and the roller speed was 3000 m / min.

[0270] Evaluation of the physical properties of fibers

[0271] The physical properties of polypropylene fibers produced using the polypropylene resin compositions prepared in Examples and Comparative Examples were evaluated, and the results are shown in Table 3 below.

[0272] (1) Fiber tenacity (unit: gf / denier)

[0273] Tenacity refers to the breaking toughness of a yarn and is measured according to ASTM D 638. The test speed is 200 mm / min, and each sample is measured six times, with the average value taken. For reference, denier is an international unit used to indicate the thickness of a fiber. 1 denier is defined as a unit weight of 1 gram per 9000 m standard length.

[0274] (2) Processability of filaments

[0275] The filament processability was evaluated according to the following criteria, which depended on the single yarn occurrence rate of the fiber during filament production.

[0276] Specifically, in the evaluation of fiber processability, when no single yarn of the fiber appeared during the drawing process, it was marked as "good", and when a single yarn of the fiber appeared during the drawing process, it was marked as "poor".

[0277] Table 3

[0278]

[0279] Referring to Table 3, in the polypropylene resin composition according to each of Examples 1 to 8 of the present invention, a propylene homopolymer (which is a polypropylene resin prepared in the presence of a metallocene compound having a specific structure) and a molecular weight modifier are used within a predetermined range to optimize all melt indices (MIs). 2.16), melting point (Tm) and crystallization temperature (Tc) and narrow weight distribution (MWD, Mw / Mn), therefore, compared with those of Comparative Examples 1 to 11, their tensile stability and orientation effect during fiber spinning are excellent, which enables stable processability during spinning while improving tenacity, and is conducive to the manufacture of spunbond nonwoven fabrics with high tenacity and ultra-low basis weight characteristics so as to minimize weight when applied to diapers, etc.

[0280] In contrast, for the polypropylene resin compositions of Comparative Examples 1 to 11, the molecular weight distribution (MWD, Mw / Mn) becomes broader, or the melt index (MI 2.16 ), melting point (Tm) and crystallization temperature (Tc) are not optimized, so it is difficult to manufacture a fiber with high tenacity suitable for ultra-low basis weight, high rigidity non-woven fabrics and with stable processability and without the risk of single yarn during spinning. In particular, due to a wider molecular weight distribution and too low melt index, Comparative Example 1 shows that single yarn fibers appear during the stretching process and shows poor spinning processability. By optimizing molecular weight distribution, Comparative Example 2 shows that single yarn fibers do not appear during the stretching process, but its melt index increases significantly, and the fiber toughness is reduced to 6.05gf / denier, so it is difficult to ensure that it is suitable for ultra-low basis weight, high rigidity non-woven fabrics. For the polypropylene resin compositions of Comparative Examples 3 to 11, the melt index is controlled within a predetermined range, but the molecular weight distribution is too narrow or too wide, and is not optimized, or the crystallization temperature is too high, making it difficult to manufacture a fiber with high tenacity suitable for ultra-low basis weight, high rigidity non-woven fabrics and without spinning defects. Especially, due to wider molecular weight distribution, the polypropylene resin compositions of Comparative Examples 3, 5, 6 and 9 show spinning defects due to the appearance of the single yarn of fiber during stretching. For Comparative Example 4, due to too narrow molecular weight distribution, spinning is not possible. The polypropylene resin compositions of Comparative Examples 7 and 8 do not show the appearance of the single yarn of fiber during stretching by controlling melt index and also by reducing the molecular weight distribution within a predetermined range, but the fiber tenacity is only 6.80gf / denier and 6.78gf / denier, showing that they are not suitable for making ultra-low basis weight, high rigidity nonwoven fabrics. Due to the rapid increase in viscosity caused by the excessive solidification of the fiber filaments caused by high crystallization temperature, the polypropylene resin composition of Comparative Example 10 shows spinning defects due to the appearance of the fiber single fiber during stretching. Due to the low viscosity caused by high melt index and wide molecular weight distribution, the polypropylene resin composition of Comparative Example 11 shows spinning defects due to the appearance of the fiber single fiber during stretching.

[0281] As described, in the polypropylene resin composition according to the present invention, the polypropylene resin prepared in the presence of a metallocene compound having a specific structure and the molecular weight modifier are used within a predetermined range, so that the melt index, melting point and crystallization temperature are optimized together with a narrow molecular weight distribution, and thus stable processability during spinning can be achieved while improving the tenacity, and polypropylene fibers suitable for ultra-low basis weight, high-rigidity non-woven fabrics can be efficiently produced so as to minimize the weight when applied to diapers and the like.

Claims

1. A polypropylene resin composition having a molecular weight distribution (Mw / Mn) of 1.7 to 2.35, Its melt index MI measured at 230°C under a load of 2.16 kg is 2.16 18g / 10min to 36g / 10min, Its melting point (Tm) is above 135°C, and Its crystallization temperature (Tc) is below 115°C. 2 . The polypropylene resin composition according to claim 1 , wherein the molecular weight distribution (Mw / Mn) of the polypropylene resin composition is 1.85 to 2.

33. 3 . The polypropylene resin composition according to claim 1 , wherein the weight average molecular weight of the polypropylene resin composition is greater than or equal to 150,000 g / mol.

4. The polypropylene resin composition according to claim 1, wherein the polypropylene resin composition has a melt index (MI) measured at 230° C. under a load of 2.16 kg. 2.16 25g / 10min to 34g / 10min. 5 . The polypropylene resin composition of claim 1 , wherein the polypropylene resin composition has a melting point (Tm) of 135 to 155° C. 6 . The polypropylene resin composition of claim 1 , wherein the polypropylene resin composition has a crystallization temperature (Tc) of 95 to 115° C.

7. The polypropylene resin composition of claim 1, wherein the polypropylene resin composition comprises a propylene homopolymer.

8. A method for preparing the polypropylene resin composition according to claim 1, comprising the steps of: preparing a polypropylene resin by polymerizing propylene monomer in the presence of a catalyst composition and hydrogen, the catalyst composition comprising one or more metallocene compounds represented by Chemical Formula 1; and melt-extruding the mixture comprising the polypropylene resin and the molecular weight modifier at a temperature of 120° C. to 300° C., The content of the molecular weight modifier is 210 ppm to 940 ppm based on the weight of the polypropylene resin: [Chemical Formula 1] In Chemical Formula 1, A is carbon, silicon or germanium, M is zirconium or hafnium, X1 and X2 are each independently halogen, R1 and R5 are each independently substituted with C 1-20 C of alkyl 6-20 Aryl, R2 to R4 and R6 to R8 are each independently hydrogen, halogen, C 1-20 Alkyl, C 2-20 Alkenyl, C 1-20 Alkylsilyl, C 1-20 Silylalkyl, C 1-20 Alkoxysilyl, C 1-20 Ether, C 1-20 Silyl ether, C 1-20 Alkoxy, C 6-20 Aryl, C 7-20 Alkyl aryl or C 7-20 Arylalkyl, R9 is replaced by C 1-20 Alkoxy or unsubstituted C 1-20 alkyl, and R 10 It is C 1-20 Alkyl or C 2-20 Alkenyl.

9. The method for preparing a polypropylene resin composition according to claim 8, wherein R1 and R5 are phenyl groups substituted with a tert-butyl group.

10. The method for preparing a polypropylene resin composition according to claim 8, wherein R9 is 6-tert-butoxyhexyl and R 10 is methyl, or R9 and R 10 All are ethyl.

11. The method for preparing a polypropylene resin composition according to claim 8, wherein the polypropylene resin is a propylene homopolymer. 12 . The method for preparing a polypropylene resin composition according to claim 8 , wherein the polypropylene resin has a molecular weight distribution (Mw / Mn) of 2.0 to 3.

0.

13. The method for preparing a polypropylene resin composition according to claim 8, wherein the polypropylene resin has a melt index (MI) measured at 230° C. under a load of 2.16 kg. 2.16 2g / 10min to 11g / 10min.

14. The method for preparing a polypropylene resin composition according to claim 8, wherein the polypropylene resin has a melting point (Tm) of 135°C or higher and a crystallization temperature (Tc) of 115°C or lower.

15. The method for preparing a polypropylene resin composition according to claim 8, wherein the molecular weight modifier is a linear acyclic organic peroxide compound.

16. The method for preparing a polypropylene resin composition according to claim 8, wherein the molecular weight modifier is one or more selected from the group consisting of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexyne and di-tert-butyl peroxide.

17. The method for preparing a polypropylene resin composition according to claim 8, wherein the mixture further comprises one or more selected from the group consisting of an antioxidant, a lubricant, a UV stabilizer and a neutralizer.

18. A polypropylene fiber comprising the polypropylene resin composition according to claim 1.

19. The polypropylene fiber of claim 18, wherein the tenacity measured according to ASTM D 638 is 6.95 gf / denier or greater.

20. A spunbonded nonwoven fabric composed of the polypropylene fiber according to claim 18.

Images