Patent Description:
In general, non-woven fabric includes fabric, felt, resin-bonded non-woven fabric, needle punch, spunbond, spunlace, emboss film, wet type non-woven fabric, and the like, which are made by bonding or entangling fiber assembly by mechanical operation or mechanical, chemical treatment such as thermal bonding without spinning and weaving, weaving, or knitting. As a specific meaning, it means bonding the contact point of randomly overlapped web and fiber with resin and using it as interlining. It is also named as bonded cloth, or bonded fabric. Such non-woven fabric may be prepared by various methods, and needle punching, chemical bonding, thermal bonding, melt bolwing, spunlace, stich bond, and spunbond methods are known.

Meanwhile, spunbond non-woven fabric using polyolefin resin as raw material has excellent feel, flexibility, air permeability, thermal insulation, and the like, and thus, is being widely used as filters, packaing materials, beddings, clothes, medical supplies, hygienic products, automobile interior materials, building materials, and the like. Particularly, polypropylene single fiber is processed into thermal-bonded non-woven fabric through calender bonding or air through bonding, due to the characteristic low melting point and excellent chemical resistance, and is mainly used as the surface material of hygienic products such as a diaper, a sanitary pad, and the like.

In <CIT>, in order to afford softness and high tensile strength, a salicylic acid salt is introduced into masterbatch pellets as a crystallization inhibitor, thus seeking softness and high tensile strength through fine denier. However, it relates to spunbond non-woven fabric and is different from thermal-bonded non-woven fabric through single fiber in terms of its preparation method. It is generally accepted that spunbond non-woven fabric exhibits high tensile strength compared to thermal-bonded non-woven fabric, but soft feel is lowered.

Further, unlike the existing homopopypropylene resin prepared using a Ziegler-Natta catalyst, homopolypropylene resin prepared using a metallocene catalyst has narrow molecular weight distribution, and thus, thin and uniform fiber can be prepared, and thus, low basis weight non-woven fabric having excellent strength can be prepared. However, since metallocene homopolypropylene resin has small content of low molecular weights, due to low xylene soluble or narrow molecular weight distribution, it has a disadvantage of giving rough surface feel when preparing non-woven fabric.

Recently, softness could be improved by using polypropylene and polyethylene as resins, and preparing non-woven fabric with different resins inside and outside of fiber by Bi-Co spinning technology. However, it is not suitable for high strength non-woven fabric due to significant deterioration of strength. Further, there has been an attempt to blend elastic polymer, for example, C3 elastomer, with polypropylene resin, but in this case, although softness can be improved, production cost increases due to expensive resin, and it is difficult to apply in industrial processes.

<CIT> relates to a metallocene compound and an olefin polymerization catalyst containing the compound intended to produce a catalyst capable of preparing an isotactic polymer.

<CIT> relates to metallocene polypropylene and filaments comprising the same.

<CIT> relates to a metallocene complex and to a catalyst comprising the metallocene complex, to a process for making polyolefins and to the use of the polyolefins for making articles.

<CIT> relates to a polypropylene-type drawn fiber, a nonwoven fabric, and its manufacturing method.

It is an object of the present invention to provide homopolypropylene resin for non-woven fabric that gives softer feel than the existing products, when used in non-woven fabric, and can realize excellent tenacity without being easily torn due to high strength, by simultaneously optimizing tacticity, molecular weight distribution (MWD), melt index (MI), melting point (Tm), and residual stress rate, and having narrow molecular weight distribution, thereby optimizing modulus.

According to one embodiment of the invention, polypropylene resin for non-woven fabric, which has tacticity of <NUM> % to <NUM> %, molecular weight distribution (MWD) of <NUM> or less, melt index (MI) of <NUM>/<NUM> to <NUM>/<NUM>, melting point (Tm) of <NUM> or less, residual stress rate of <NUM> % or less, is provided.

The homopolypropylene resin for non-woven fabric may have molecular weight distribution (MWD) of <NUM> to <NUM>, melting point (Tm) of <NUM> to <NUM>, tacticity of <NUM> % to <NUM> %, and melt index (MI) of <NUM>/<NUM> to <NUM>/<NUM>.

And according to another embodiment of the invention, a method for preparing homopolypropylene resin for non-woven fabric is provided, which comprises a step of polymerizing propylene in the presence of a single catalyst comprising only a transition metal compound represented by the following Chemical Formula <NUM> as a catalytically active ingredient. <CHM>
<CHM>
in the Chemical Formula <NUM>,.

For example, in the Chemical Formula relating to the transition metal compound, R<NUM> and R<NUM>, and R<NUM> and R<NUM> may be respectively connected with each other to form C<NUM>-<NUM> aryl.

The transition metal compound may be represented by the following Chemical Formula <NUM>-<NUM>. <CHM>
<CHM>
in the Chemical Formula <NUM>-<NUM>,
A, M, X<NUM>, X<NUM> , R<NUM>, R<NUM>, R<NUM>, R<NUM> , R<NUM>, R<NUM>, R<NUM>, and R<NUM> are as defined in the Chemical Formula <NUM>.

In the Chemical Formula <NUM> relating to the transition metal compound, A may be silicon; M may be zirconium or hafnium; X<NUM> and X<NUM> may be each independently, halogen; R<NUM> and R<NUM> may be each independently, hydrogen, or C<NUM>-<NUM> linear alkyl; R<NUM>, R<NUM>, R<NUM>, and R<NUM> may be hydrogen; and R<NUM> and R<NUM> may be identical to each other, and may be C<NUM>-<NUM> linear alkyl.

The transition metal compound may be represented by one of the following Structural Formulas:
<CHM>.

Further, the polymerization step may be conducted by a continuous type bulk-slurry polymerization process.

According to the present invention, metallocene homopolypropylene resin that is prepared in the presence of a single catalyst comprising a specific transition metal compound, and has optimized tacticity, molecular weight distribution (MWD), melt index (MI), melting point (Tm) and residual stress rate, and narrow molecular weight distribution, and thus, gives softer feel than the existing products and has excellent tenacity without being easily torn due to high strength, is provided.

Hereinafter, homopolypropylene resin for non-woven fabric and a method for preparing the same according to specific embodiments of the invention will be explained.

First, technical terms in the present specification are only for mentioning specific embodiments, and they are not intended to restrict the present invention unless there is a particular mention about them. A singular expression includes a plural expression thereof, unless it is expressly stated or obvious from the context that such is not intended. Further, the meaning of the term "comprise" or "contain" used in the specification embodies specific characteristics, areas, essences, steps, actions, elements, and/or components, and does not exclude existence or addition of other specific characteristics, areas, essences, steps, actions, elements, components, and/or groups.

As used herein, terms "a first", "a second" and the like are used to explain various constructional elements, and they are used only to distinguish one constructional element from other constructional elements.

Further, the terms used herein are only to explain specific embodiments, and are not intended to limit the present invention. A singular expression includes a plural expression thereof, unless it is expressly stated or obvious from the context that such is not intended. As used herein, the terms "comprise" or "have", etc. are intended to designate the existence of practiced characteristic, number, step, constructional element or combinations thereof, and they are not intended to preclude the possibility of existence or addition of one or more other characteristics, numbers, steps, constructional elements or combinations thereof.

Although various modifications can be made to the present invention and the present invention may have various forms, specific examples will be illustrated and explained in detail below. However, it should be understood that these are not intended to limit the present invention to specific disclosure, and that the present invention is as set out in the appended claims.

Hereinafter, the present invention will be explained in detail.

According to one embodiment of the invention, polypropylene resin for non-woven fabric, which has tacticity of <NUM> % to <NUM> %, molecular weight distribution (MWD) of <NUM> or less, melt index (MI) of <NUM>/<NUM> to <NUM>/<NUM>, melting point (Tm) of <NUM> or less, and residual stress rate of <NUM> % or less, is provided.

The present inventors confirmed during studies on polypropylene resin used for non-woven fabric that previously known metallocene homopolypropylene resin has small content of low molecular weights due to low xylene solubles or narrow molecular weight distribution, and thus, it has a disadvantage of giving tough surface feel when prepared into non-woven fabric.

Thus, the present inventors confirmed during repeated studies for improving the above problem that by optimizing tacticity of metallocene homopolypropylene resin to <NUM> % to <NUM> %, optimizing melt index (MI) to <NUM> to <NUM>/<NUM>, optimizing melting point (Tm) to <NUM> or less, and simultaneously, optimizing residual stress rate and molecular weight distribution respectively to <NUM> % or less and <NUM> or less, thus optimizing modulus, non-woven fabric having softer feel than the existing products and having excellent tenacity can be prepared.

Particularly, if soft non-woven fabric is prepared by lowering tacticity by the existing method, although soft property may be realized, strength of non-woven fabric may decrease, and thus, it may be easily torn. This is because the molecular weight distribution of resin is wide and it is difficult to sufficiently draw in the processing process. Thus, in the present invention, by comprising homopolypropylene resin obtained by a polymerization process using a single catalyst comprising a specific metallocene catalyst as an active ingredient instead of a Ziegler-Natta catalyst, tacticity may be lowered and low molecular weight distribution of <NUM> or less may be realized, thereby simultaneously realizing softness and high strength. In the present invention, softness and high strength, which are the properties in trade-off relationship, can be realized, by comprising homopolypropylene resin prepared through a reactor-made process using a single catalyst.

The homopolypropylene resin according to the present invention can be used for preparing non-woven fabric, and it is characterized in that the tacticity of metallocene homopolypropylene resin is <NUM> % to <NUM> %.

The tacticity of the homopolypropylene resin can be measured through NMR (nuclear magnetic resonance) analysis, and it may be <NUM> % to <NUM> %. Here, the tacticity may be a value measured using NMR (nuclear magnetic resonance) instrument. The measurement method of tacticity will be explained in detail in the experimental examples described below. The tacticity of the resin should be <NUM> % or more so as to secure excellent tenacity when preparing non-woven fabric, and it should be <NUM> % or less so as to realize non-woven fabric having softness.

The homopolypropylene resin of the present invention is characterized by having narrow molecular weight distribution (MWD) of <NUM> or less, as well as optimized tacticity as explained above.

The molecular weight distribution of the homopolypropylene resin may be <NUM> or less, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>. Here, the homopolypropylene resin should have narrow molecular weight distribution (MWD) of <NUM> or less so as to secure excellent tenacity when preparing non-woven fabric.

In the present invention, the molecular weight distribution is measured by measuring the weight average molecular weight (Mw) and number average molecular weight (Mn) of homopolypropylene resin, respectively, using gel permeation chromatography (GPC), and calculating the rate of the weight average molecular weight to the number average molecular weight (Mw/Mn).

Specifically, it can be measured using Waters PL-GPC220 as a gel permeation chromatography (GPC) device, and using Polymer Laboratories PLgel MIX-B <NUM> length column. Here, the measurement temperature is <NUM>, <NUM>,<NUM>,<NUM>-trichlorobenzene is used as a solvent, and the flow rate is set to1 mL/min. Further, the sample of homopolypropylene resin is prepared at the concentration of <NUM>/<NUM>, and fed in an amount of <NUM>µL. Using a calibration curve formed using a polystyrene standard specimen, Mw and Mn can be derived. Here, as the polystyrene standard specimen, <NUM> kinds having weight average molecular weight of <NUM>/mol, <NUM>/mol, <NUM>/mol, <NUM>/mol, <NUM>/mol, <NUM>/mol, <NUM>/mol, <NUM>/mol, <NUM>/mol may be used.

Further, the homopolypropylene resin of the present invention is characterized by optimized melt index (MI) of <NUM>/<NUM> to <NUM>/<NUM> and melting point (Tm) of <NUM> or less, as well as optimized taciticity range and narrow molecular weight distribution as explained above.

The melt index (MI) of the homopolypropylene resin may be <NUM>/<NUM> to <NUM>/<NUM>, or <NUM>/<NUM> to <NUM>/<NUM>, or <NUM>/<NUM> to <NUM>/<NUM>, when measured at <NUM> under load of <NUM> according to ASTM (American society for testing and materials) standard of ASTM D <NUM>. Here, the melt index (MI) should be maintained within the above range so as to simultaneously secure excellent spinnability and strength of non-woven fabric. Particularly, when processing non-woven fabric using resin, if melt index (MI) is less than <NUM>/<NUM>, processing pressure may increase and processibility may be deteriorated. Further, if the melt index (MI) exceeds <NUM>/<NUM>, although pressure may be secured during processing, high strength of the product as desired may not be realized.

Further, the melting point (Tm) of the homopolypropylene resin may be <NUM> or less, or <NUM> to <NUM>, or <NUM> or less, or <NUM> to <NUM>, or <NUM> or less, or <NUM> to <NUM>. Particularly, the melting point (Tm) of the homopolypropylene resin should be <NUM> or less so as to secure softness when processed into fiber for non-woven fabric and prevent degradation of resin due to increase in processing temperature. Further, if the melting point (Tm) of the homopolypropylene resin exceeds <NUM>, spinnability may be deteriorated to generate breakage, and thus, defect rate may increase. However, if the melting point (Tm) of the homopolypropylene resin is <NUM> or less, there may be a difficulty in producing resin or productivity may be lowered.

Meanwhile, in the present invention, the melting point of homopolypropylene resin may be measured by increasing the temperature of the homopolypropylene resin to <NUM>, maintaining that temperature for <NUM> minutes, decreasing temperature to <NUM>, and then, increasing temperature again, and defining the top of the DSC (Differential Scanning Calorimeter, manufactured by TA Instruments) curve as the melting point. Here, temperature increase and decrease rates are respectively <NUM>/min, and the melting point is the result measured in the second temperature increase section.

In addition, the homopolypropylene resin is characterized by narrow residual stress rate of <NUM> %, as well as the above explained tacticity, molecular weight distribution, melt index, and melting point (Tm).

The residual stress rate may be <NUM> % or less, or <NUM> % to <NUM> %, or <NUM> % or less, or <NUM> % to <NUM> %, or <NUM> % or less, or <NUM> % to <NUM> %.

Particularly, the residual stress rate can confirm fiber processability through rheological property test under an environment similar to a non-woven fabric manufacturing process, and it is measured according to the following Calculation Formula <NUM> by applying large strain to the homopolypropylene resin and conducting stress relaxation test.

In the Calculation Formula <NUM>, RS<NUM> is residual stress at one time point (t<NUM>) of less than <NUM> seconds after applying <NUM> % strain to the homopolypropylene resin, and RS<NUM> is residual stress at one time point (t<NUM>) between <NUM> seconds to <NUM> seconds after applying <NUM> % strain to the homopolypropylene resin.

Namely, according to one embodiment of the invention, if the residual stress rate according to the Calculation Formula <NUM> exceeds <NUM> %, when conducting melt blowing of the polypropylene resin, a possibility of generating breakage may be too high, thus increasing defect rate when preparing non-woven fabric. The residual stress rate should be maintained at <NUM> % or less, or <NUM> % or less, or <NUM> % or less, so as to minimize breakage when processing non-woven fabric. Particularly, fiber is spun in a molten state and drawn in a semi-molten state through cooling, but if residual stress is high, a tendency to shrink may increase, thus increasing the possibility of generating breakage.

In the Calculation Formula <NUM>, RS<NUM> denotes residual stress immediately after applying <NUM> % strain to the homopolypropylene resin, for example, at one time point (t<NUM>) of less than <NUM> seconds, under <NUM>. Further, in the Calculation Formula <NUM>, RS<NUM> denotes residual stress within <NUM> seconds after the t<NUM> [for example, at one time point (t<NUM>) between <NUM> seconds to <NUM> seconds], under the same condition as the RS<NUM>.

Specifically, in the Calculation Formula <NUM>, the t<NUM> may be selected from <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds. Further, in the Calculation Formula <NUM>, the t<NUM> may be selected from <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds.

Preferably, in order to easily secure available data when measuring residual stress, it may be advantageous that t<NUM> is <NUM> seconds, and t<NUM> is <NUM> second, in the Calculation Formula <NUM>.

Further, the residual stress rate of the homopolypropylene resin is measured under a similar environment (for example, <NUM>) to the process condition for conducting melt blowing when preparing non-woven fabric. The temperature of <NUM> corresponds to a temperature suitable for completely dissolving homopolypropylene resin to conduct melt blowing.

In the homopolypropylene resin of the present invention, it is preferable that molecular weight distribution (MWD) is also maintained in a low range as explained above so as to maintain residual stress rate within the above explained optimum range and secure excellent fiber processability.

Since the homopolypropylene resin according to one embodiment of the invention has narrow molecular weight distribution, as well as optimized tacticity, molecular weight distribution (MWD), melt index (MI), melting point Tm), and residual stress rate, when used for non-woven fabric, it can give softer feel than the existing products and realize excellent tenacity without being easily torn due to high strength.

The homopolypropyleneresin for non-woven fabric according to one embodiment of the invention, having the above properties and constructional characteristics, may be prepared by a method comprising a step of polymerizing propylene in the presence of a single catalyst comprising only a transition metal compound represented by the following Chemical Formula <NUM> as a catalytically active ingredient. Thus, according to another embodiment of the invention, a method for preparing the above explained homopolypropylene resin for non-woven fabric is provided. <CHM>
in the Chemical Formula <NUM>,.

In the specification, the following terms may be defined as follows unless specifically limited.

Halogen may be fluorine (F), chlorine (Cl), bromine (Br) or iodine (I).

A C<NUM>-<NUM> alkyl, namely, an alkyl group having a carbon number of <NUM> to <NUM> may be a linear, branched or cyclic alkyl group. Specifically, the C1-<NUM> alkyl group may be a C1-<NUM> linear alkyl group; a C1-<NUM> linear alkyl group; a C1-<NUM> linear alkyl group; a C3-<NUM> branched or cyclic alkyl group; a C3-<NUM> branched or cyclic alkyl group; or a C3-<NUM> branched or cyclic alkyl group. More specifically, the C1-<NUM> alkyl group may be a methyl, an ethyl, an n-propyl, an iso-propyl, an n-butyl, an iso-butyl, a tert-butyl, an n-pentyl, an iso-pentyl, a neo-pentyhl, or a cyclohexyl group.

A C<NUM>-<NUM> alkoxy, namely, an alkoxy group having a carbon number of <NUM> to <NUM> means C1-<NUM> linear or branched alkyl group bonded with oxygen (-OR). Specifically, the alkoxy group includes a C1-<NUM>, more specifically, a C1-<NUM> alkoxy group. As specific examples of the alkoxy group, a methoxy, an ethoxy, a propoxy, a butoxy, or a t-butoxy group may be mentioned.

A C<NUM>-<NUM> alkoxyalkyl, namely, an alkoxyalkyl group having a carbon number of <NUM> to <NUM> means a functional group in which the above explained alkoxy group is substituted at the carbon of a linear or branched alkyl group instead of hydrogen. Specifically, the alkoxyalkyl group includes a C2-<NUM>, more specifically, a C2-<NUM> alkoxyalkyl group. As specific examples of the alkoxyalkyl group, a methoxymethyl, a tert-butoxymethyl, a tert-butoxyhexyl, <NUM>-ethoxyethyl, or <NUM>-methyl-<NUM>-methoxyethyl group may be mentioned.

A C<NUM>-<NUM> alkenyl, namely, an alkenyl group having a carbon number of <NUM> to <NUM> may be a linear, branched or cyclic alkenyl group. Specifically, the C2-<NUM> alkenyl group may be a C2-<NUM> linear alkenyl group, a C2-<NUM> linear alkenyl group, a C2-<NUM> linear alkenyl group, a C3-<NUM> branched alkenyl group, a C3-<NUM> branched alkenyl group, a C3-<NUM> branched alkenyl group, a C5-<NUM> cyclic alkenyl group, or a C5-<NUM> cyclic alkenyl group. More specifically, the C2-<NUM> alkenyl group may be an ethenyl, a propenyl, a butenyl, a pentenyl, or a cyclohexenyl group.

A C<NUM>-<NUM> cycloalkyl, namely, a cycloalkyl group having a carbon number of <NUM> to <NUM> means a C3-<NUM> cyclic saturated hydrocarbon group. Specifically, the cycloalkyl group includes a C3-<NUM> cycloalkyl group. As specific examples of the cycloalkyl group, a cyclopropyl, a cyclobutyl, or a cyclohexyl group may be mentioned.

A C<NUM>-<NUM> aryl, namely, an aryl group having a carbon number of <NUM> to <NUM> may mean monocyclic, bicyclic or tricyclic aromatic hydrocarbon. Specifically, the C6-<NUM> aryl group may be a phenyl, a naphthyl, or an anthracenyl group.

A C<NUM>-<NUM> alkylaryl, namely, an alkylaryl group having a carbon number of <NUM> to <NUM> may mean a substituent group in which one or more hydrogen atoms of aryl are substituted with alkyl. Specifically, C7-<NUM> alkylaryl may be methylphenyl, ethylphenyl, n-propylphenyl, iso-propylphenyl, n-butylphenyl, iso-butylphenyl, tert-butylphenyl or cyclohexylphenyl.

A C<NUM>-<NUM> arylalkyl, namely, an arylalkyl group having a carbon number of <NUM> to <NUM> may mean a substituent in which one or more hydrogen atoms of alkyl are substituted with aryl. Specifically, the C7-<NUM> arylalkyl may be a benzyl, a phenylpropyl or a phenylhexyl group.

A C<NUM>-<NUM> aryloxy, namely, an aryloxy group having a carbon number of <NUM> to <NUM> means an aryl group bonded with oxygen (OAr), wherein the aryl group is as defined above. Specifically, the aryloxy group includes a C6-<NUM>, more specifically, a C6-<NUM> aryloxy group. As specific examples of the aryloxy group, a phenoxy group may be mentioned.

A silyl group means a -SiHs radical derived from silane, wherein one least one hydrogen atoms in the silyl group may be substituted with various organic groups such as an alkyl group, an alkoxy, group, or a halogen group. Here, the alkyl group, alkoxy group, and halogen group are as defined above.

A nitro group means a -NO<NUM> radical in which one nitrogen atom and two oxygen atoms are bonded.

A C<NUM>-<NUM> sulfonate, namely, a sulfonate group having a carbon number of <NUM> to <NUM> means a functional group in which hydrogen of a sulfonic acid group (-SOsH) is substituted with an alkyl group, wherein the alkyl group is as defined above. Specifically, the sulfonate group may be -SOsR (wherein, R is a C1-<NUM> linear or branched alkyl group).

An amido group means an amino group bonded to a carbonyl group (C=<NUM>)
A C<NUM>-<NUM> alkylamino, namely, an alkylamino group having a carbon number of <NUM> to <NUM> means a functional group in which at least one hydrogen atoms of an amino group (-NH<NUM>) are substituted with an alkyl group, wherein the alkyl group is as defined above. Specifically, the alkylamino group may be -NR<NUM> (wherein, each of R's may be a hydrogen atom or a C1-<NUM> linear or branched alkyl group, provided that both R's are not a hydrogen atoms).

A C<NUM>-<NUM> arylamino, namely, an arylamino group having a carbon number of <NUM> to <NUM> means a functional group in which at least one hydrogen atoms of an amino group (-NH<NUM>) are substituted with an aryl group, wherein the aryl group is as defined above.

A C<NUM>-<NUM> aliphatic or aromatic ring, namely, an aliphatic or aromatic ring having a carbon number of <NUM> to <NUM> means a cycloalkyl or an aryl group, wherein the cycloalkyl group and aryl group are as defined above.

A C<NUM>-<NUM> silylalkyl, namely, a silylalkyl group having a carbon number of <NUM> to <NUM> means a functional group in which at least one hydrogen atoms of an alkyl group are substituted with a silyl group, wherein the alkyl group and silyl group are as defined above.

C<NUM>-<NUM> ether, namely, ether having a carbon number of <NUM> to <NUM> means a hydrocarbyl group including a -O- radical, wherein at least one hydrogen atoms in the ether group may be substituted with various organic groups such as silyl group. Wherein the silyl group is as defined above.

An alkylidene group means a divalent aliphatic hydrocarbon group in which two hydrogen atoms are removed from the same carbon atom of an alkyl group. Specifically, the alkylidene group includes a C1-<NUM>, more specifically, a C1-<NUM> alkylidene group. As specific examples of the alkylidene group, a propane-<NUM>-ylidene group may be mentioned.

An arylene group means a divalent aromatic hydrocarbon group in which two hydrogen atoms are removed from the same carbon atom of an aryl group. Specifically, the arylene group includes a C6-<NUM>, more specifically, a C6-<NUM> arylene group. As specific examples of the arylene group, a phenylene group may be mentioned.

A hydrocarboyl group means a monovalent hydrocarbon group having a carbon number of <NUM> to <NUM>, consisting only of carbon and hydrogen, irrespective of the structure, such as an alkyl, an aryl, an alkenyl, an alkylaryl, or an arylakyl group.

Further, unless specifically defined in the specification, 'a combination thereof' means that two or more functional groups are bonded by a single bond, a double bond (ethylene group), a triple bond (acetylene group), or a linking group such as a C1-<NUM> alkylene group (for example, methylene group (-CH<NUM>-) or ethylene group (-CH<NUM>CH<NUM>-)), or two more functional groups are condensed and linked.

Particularly, the present invention is characterized by using a single catalyst comprising a transition metal compound of the above Chemical Formula <NUM> as a single component, instead of a hybrid catalyst suitable for processing such as injection due to wide molecular weight distribution, in order to prepare homopolypropylene resin for non-woven fabric that is soft but has excellent strength.

Further, in the existing process, two kinds of resins having different properties may be mixed to prepare non-woven fabric, while in the present invention, softness and strength can be simultaneously fulfilled with one kind of resin prepared by a reactor-made process.

The homopolypropylene may be prepared by a polymerization process of contacting a catalyst comprising a transition metal compound represented by the Chemical Formula <NUM> with propylene.

Further, according to one embodiment of the invention, the homopolymerization of propylene may be conducted under hydrogen gas. Here, the hydrogen gas may be introduced such that the amount became <NUM> ppm or less, or <NUM> ppm to <NUM> ppm, or <NUM> ppm to <NUM> ppm, based on the total weight of propylene. By controlling the amount of hydrogen gas used, sufficient catalytic activity may be exhibited, and simultaneously, the molecular weight distribution and flowability of prepared homopolypropylene resin may be controlled within desired ranges, thereby preparing propylene-butene copolymer having appropriate properties according to use.

As a transition metal compound used as a catalyst for preparing the homopolypropylene resin, one or more kinds of transition metal compounds represented by the Chemical Formula <NUM> may be used.

In the Chemical Formula <NUM>, R<NUM> and R<NUM>, and R<NUM> and R<NUM> may be respectively connected with each other to form C<NUM>-<NUM> aryl.

In the Chemical Formula <NUM>, A may be silicon (Si).

In the Chemical Formula <NUM>, M may be zirconium (Zr) or hafnium (Hf).

In the Chemical Formula <NUM>, each of X<NUM> and X<NUM> may be halogen. Specifically, each of X<NUM> and X<NUM> may be chloro.

In the Chemical Formula <NUM>, each of R<NUM> and R<NUM> may be hydrogen or C<NUM>-<NUM> linear alkyl, or hydrogen or methyl.

In the Chemical Formula <NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> may be hydrogen.

In the Chemical Formula <NUM>, R<NUM> and R<NUM> may be identical to each other, and may be a C<NUM>-<NUM> linear alkyl group.

In the Chemical Formula <NUM>, R<NUM> may be ethyl or <NUM>- (t-butoxy)-hexyl.

For example, as the transition metal compound, a transition metal compound of the Chemical Formula <NUM> wherein A is silicon; M is Zr or Hf; each of X<NUM> and X<NUM> is halogen; each of R<NUM> and R<NUM> is hydrogen or methyl; R<NUM> and R<NUM>, and R<NUM> and R<NUM> are respectively connected with each other to form C<NUM>-<NUM> aryl; R<NUM>, R<NUM>, R<NUM>, and R<NUM> are hydrogen; R<NUM> and R<NUM> are identical to each other, and C<NUM>-<NUM> linear alkyl group, may be used.

Further, according to specific embodiment, the transition metal compound may be represented by the following Chemical Formula <NUM>-<NUM>. <CHM>
In the Chemical Formula <NUM>-<NUM>,
A, M, X<NUM>, X<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> are as defined in the Chemical Formula <NUM>.

The transition metal compound of the above structure may cause appropriate steric hindrance to secure the above explained effects more effectively.

Here, the substituents of the silicon bridge, R<NUM> and R<NUM>, may be identical to each other and each may be a C<NUM>-<NUM> alkyl group, more specifically, a C<NUM>-<NUM> linear alkyl group, more specifically, an ethyl group, so as to increase solubility and improve support efficiency. In case a methyl group is included as the substituent of the bridge, when preparing a supported catalyst, solubility may not be good, and thus, support reactivity may be lowered.

Further, as the center metal of the catalyst, Zr and Hf are preferable, wherein Zr increases the activity, and Hf increases the melting point (Tm) of produced resin by <NUM> to <NUM>, and thus, they can be appropriately applied according to use.

Preferably, the transition metal compound may be represented by one of the following Structural Formulas:
<CHM>.

The transition metal compound represented by the Chemical Formula <NUM> may be synthesized applying known reactions, and for more detailed synthesis method, Preparation Examples <NUM> to <NUM> described below may be referred to.

Meanwhile, a catalyst comprising the transition metal compound having the structure of the Chemical Formula <NUM> may further comprise various cocatalysts so as to acheive high activity and improve process stability. As the cocatalyst compound, one or more compounds represented by the following Chemical Formula <NUM> or Chemical Formula <NUM> may be included.

[Chemical Formula <NUM>]     R<NUM>-[Al (R<NUM>)-O]m-R<NUM>.

For example, in the present invention, various cocatalysts represented by the Chemical Formula <NUM> or Chemical Formula <NUM> may be used as the cocatalyst. For example, as the cocataylst of the Chemical Formula <NUM>, methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, tert-butyl aluminoxane or a mixture thereof may be used. Further, as the cocataylst of the Chemical Formula <NUM>, trimethylammonium tetrakis (pentafluorophenyl)borate, triethylammonium tetrakis (pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis (pentafluorophenyl)borate, N,N-dimethylanilinium n-butyltris (pentafluorophenyl)borate, N,N-dimethylanilinium benzyltris (pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis (<NUM>- (t-butyldimethylsilyl)-<NUM>,<NUM>,<NUM>,<NUM>-tetrafluorophenyl)borate, N,N-dimethylanilinium tetrakis (<NUM>- (triisopropylsilyl)-<NUM>,<NUM>,<NUM>,<NUM>-tetrafluorophenyl)borate, N,N-dimethylanilinium pentafluorophenoxytris (pentafluorophenyl)borate, N,N-dimethyl-<NUM>,<NUM>,<NUM>-trimethylanilinium tetrakis (pentafluorophenyl)borate, trimethylammonium tetrakis (<NUM>,<NUM>,<NUM>,<NUM>-tetrafluorophenyl)borate, N,N-dimethylanilinium tetrakis (<NUM>,<NUM>,<NUM>,<NUM>-tetrafluorophenyl)borate, hexadecyldimethylammonium tetrakis (pentafluorophenyl)borate, N-methyl-N-dodecylanilinium tetrakis (pentafluorophenyl)borate or methyldi (dodecyl)ammonium tetrakis (pentafluorophenyl)borate, and mixtures thereof may be used.

The content of the cocatalyst used may be appropriately controlled according to the aimed properties or effects of the catalyst and homopolypropylene resin.

Further, the catalyst comprising the transition metal compound having the structure of the Chemical Formula <NUM> may be used in the form of a supported catalyst wherein the transition metal compound of the Chemical Formula <NUM>, and according to circumstances, the cocatalyst of the Chemical Formula <NUM> or Chemical Formula <NUM> are supported in a catalyst support.

As the catalyst support, those containing a hydroxyl group or a siloxane group on the surface may be used. Specifically, as the catalyst support, those containing highly reactive hydroxyl group or siloxane group, obtained by drying at high temperature to remove moisture on the surface, may be used. More specifically, as the catalyst support, silica, alumina, magnesia or a mixture thereof may be used. The catalyst support may be dried at high temperature, and may commonly comprise oxide, carbonate, sulfate, nitrate components such as Na<NUM>O, K<NUM>CO<NUM>, BaSO<NUM> and Mg (NO<NUM>)<NUM>,.

The supported catalyst may be formed by sequentially supporting the cocatalyst of the Chemical Formula <NUM>, the transition metal compound of the Chemical Formula <NUM>, and the cocatalyst of the Chemical Formula <NUM> on the catalyst support. The supported catalyst having a structure determined according to the sequence of supporting may realize high activity and excellent process stability during the preparation process of homopolypropylene resin.

More specifically, the supported catalyst may be a single supported catalyst comprising only a transition metal compound represented by the Chemical Formula <NUM> as a catalytically active ingredient.

The homopolypropylene resin may be prepared by a continuous polymerization process, and various polymerization processes known as the polymerization reaction of olefin monomers, such as continuous type solution polymerization, continuous type bulk polymerization, continuous type suspension polymerization, continuous type slurry polymerization, or continuous type emulsion polymerization may be adopted. However, in order to obtain uniform molecular weight distribution as explained above and prepare homopolypropylene resin suitable for nonwoven fabric fiber, continuous type bulk-slurry polymerization is preferable.

Specifically, the polymerization reaction may be conducted at a temperature of <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>. Further, the polymerization process may be conducted under pressure range known in the field of polypropylene resin preparation, for example, under pressure of <NUM> to <NUM> kgf/cm<NUM>. For example, although varies according to the size of a practical reactor, the continuous type polymerization process may be conducted with the propylene input amount of <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM> per hour.

Further, in the polymerization reaction, the catalyst may be used while being dissolved or diluted in a solvent such as pentane, hexane, heptanes, nonane, decane, toluene, benzene, dichloromethane, or chlorobenzene. Here, a small amount of water or air that may have an adverse influence on the catalyst may be previously removed by treating the solvent with a small amount of alkylaluminum. For example, the catalyst may be used in the form of a mud catalyst mixed with oil or grease, and the content of the catalyst may be <NUM> % to <NUM> %, or <NUM> % to <NUM> %, or <NUM> % to <NUM> %, based on the total weight comprising oil, or grease.

Since the method for preparing homopolypropylene resin according to another embodiment of the invention uses a single catalyst comprising only a transition metal compound represented by the Chemical Formula <NUM> as a catalytically active ingredient, the prepared homopolypropylene resin may have optimized tacticity, molecular weight distribution (MWD), melt index (MI), melting point (Tm), and residual stress rate, and simultaneously, have narrow molecular weight distribution, and thus, when used for non-woven fabric, can give softer feel than the existing products, and realize excellent tenacity without being easily torn due to high strength.

Thus, according to yet another embodiment of the present invention, a resin composition for non-woven fabric comprising the above explained homopolypropylene resin, and a non-woven fabric product prepared using the same are provided.

Specifically, the resin composition for non-woven fabric may comprise masterbatch additives such as Exolit OP <NUM> together with the above explained homopolypropylene resin, and it may be prepared by a method comprising the steps of mixing masterbatch additives with the homopolypropylene resin and extruding the mixture.

Further, the extrusion process for preparing the resin composition may be conducted according to a common method. For example, it may be conducted under conditions of <NUM> to <NUM>, <NUM> rpm to <NUM> rpm, using an extruder such as a <NUM> twin-screw extruder.

Since the resin composition comprises the above explained homopolypropylene resin, it may have optimized tacticity, molecular weight distribution (MWD), melt index (MI), melting point (Tm) and residual stress rate, and simultaneously, have narrow molecular weight distribution, and thus, it may be useful for a resin composition for non-woven fabric capable of simultaneously realizing softness and high strength, which are in trade-off relationship, when preparing non-woven fabric.

Meanwhile, the present invention provides non-woven fabric prepared using the resin composition, and the non-woven fabric may be spunbond non-woven fabric prepared by a melt blowing process.

Specifically, the non-woven fabric may be prepared by feeding the molten resin composition to a melt pump (<NUM> rpm), and then, feeding it to a melt blowing die equipped with an outlet, thereby extruding into a ultrafine fiber web, using a Brabender conical type twin screw extruder. Here, the melt blowing process may be conducted at a melting temperature of <NUM>, screw speed of <NUM> rpm, die temperature of <NUM>, primary air temperature and pressure of <NUM> and <NUM> kPa (<NUM> psi), polymer treatment speed of <NUM>/hr, and collector/die distance of <NUM>.

Hereinafter, preferable examples are presented for better understanding of the present invention. However, these examples are presented only as the illustrations of the present invention as set out in the appended claims.

<NUM>-methyl-<NUM>,<NUM>-benzoindene (<NUM>) was dissolved in a toluene/THF=<NUM>/<NUM> solution (<NUM>), and an n-butyllithium solution (<NUM>, hexane solvent, <NUM>) was slowly added dropwise at <NUM>, and then, the solution was stirred at room temperature for a day. Thereafter, diethyldichlorosilane (<NUM>) was slowly added dropwise to the mixed solution at -<NUM>, and the solution was stirred for <NUM> minutes, and then, stirred at room temperature for a day. Thereafter, water was added to separate an organic layer, and then, the solvent was distilled under reduced pressure to obtain (diethylsilane-diyl)-bis (<NUM>-methyl-<NUM>,<NUM>-benzoindenyl)silane.

(Diethylsilane-diyl)-bis (<NUM>-methyl-<NUM>,<NUM>-benzoindenyl)silane prepared in the step <NUM> was dissolved in a toluene/THF=<NUM>/<NUM> solution (<NUM>), an n-butyllithium solution (<NUM>, hexane solvent, <NUM>) was slowly added dropwise at -<NUM>, and then, the solution was stirred for a day. To the reaction solution, hafnium chloride (<NUM>) diluted in toluene (<NUM>) was slowly added dropwise at -<NUM>, and the solution was stirred at room temperature for a day. The solvent of the reaction solution was removed under reduced pressure, dichloromethane was put and the solution was filtered, and then, the filtrate was distilled under reduced pressure and removed. By recrystallization with toluene and hexane, high purity rac-[(diethylsilane-diyl)-bis (<NUM>-methyl-<NUM>,<NUM>-benzoindenyl)]hafnium dichloride (<NUM>, <NUM> %, rac:meso=<NUM>:<NUM>) was obtained.

Into a <NUM> reactor, <NUM> of silica and <NUM> wt% methylaluminoxane (<NUM>) were put, and the mixture was reacted at <NUM> for <NUM> hours. After precipitation, the upper part was removed, and the remaning part was washed with toluene two times. The ansa-metalocene compound rac-[(diethylsilane-diyl)-bis (<NUM>-methyl-<NUM>,<NUM>-benzoindenyl)]hafnium dichloride (<NUM>) prepared in the step <NUM>) was diluted in toluene and added to a reactor, and then, reacted at <NUM> for <NUM> hours. After the completion of the reaction, when precipitation was finished, the upper part solution was removed, and the remaining reaction product was washed with toluene, washed with hexane again, and vacuum dried to obtain <NUM> of silica supported metallocene catalyst in the form of solid particles.

(Diethylsilane-diyl)-bis (<NUM>-methyl-<NUM>,<NUM>-benzoindenyl)silane prepared in the step <NUM> was dissolved in a toluene/THF=<NUM>/<NUM> solution (<NUM>), an n-butyllithium solution (<NUM>, hexane solvent, <NUM>) was slowly added dropwise at -<NUM>, and then, the solution was stirred for a day. To the reaction solution, zicronium chloride (<NUM>) diluted in toluene (<NUM>) was slowly added dropwise at -<NUM>, and the solution was stirred at room temperature for a day. The solvent of the reaction solution was removed under reduced pressure, dichloromethane was put and the solution was filtered, and then, the filtrate was distilled under reduced pressure and removed. By recrystallization with toluene and hexane, high purity rac-[(diethylsilane-diyl)-bis (<NUM>-methyl-<NUM>,<NUM>-benzoindenyl)]zirconium dichloride (<NUM>, <NUM> %, rac:meso=<NUM>:<NUM>) was obtained.

Into a <NUM> reactor, <NUM> of silica and <NUM> wt% methylaluminoxane (<NUM>) were put, and the mixture was reacted at <NUM> for <NUM> hours. After precipitation, the upper part was removed, and the remaining part was washed with toluene two times. The ansa-metalocene compound rac-[(diethylsilane-diyl)-bis (<NUM>-methyl-<NUM>,<NUM>-benzoindenyl)]zirconium dichloride (<NUM>) prepared in the step <NUM>) was diluted in toluene and added to a reactor, and then, reacted at <NUM> for <NUM> hours. After the completion of the reaction, when precipitation was finished, the upper part solution was removed, and the remaining reaction product was washed with toluene, washed with hexane again, and vacuum dried to obtain <NUM> of silica supported metallocene catalyst in the form of solid particles.

A silica supported metallocene catalyst in the form of solid particles was prepared by the same method as the step <NUM>) of Preparation Example <NUM>, using a transition metal compound represented by the following Chemical Formula A and [(<NUM>-t-butoxyhexylmethylsilane-diyl)-bis (<NUM>-methyl-<NUM>-tert-butylphenylindenyl)]zirconium chloride.

In the Chemical Formula A, tBu denotes tert-butyl (tertiary butyl).

A supported catalyst was prepared by the same method as the step <NUM>) of Preparation Example <NUM>, using a transition metal compound represented by the following Chemical Formula B and [(<NUM>-t-butoxyhexylmethylsilane-diyl)-bis (<NUM>-methyl-<NUM>-tert-butylphenylindenyl)]zirconium chloride. <CHM>
<CHM>.

A hybrid supported catalyst was prepared using [(<NUM>-t-butoxyhexyl) (methyl)silane-diyl)-bis (<NUM>-methyl-<NUM>, <NUM>-benzoindenyl)]zirconium dichloride prepared according to the steps <NUM>) and <NUM>) of Comparative Example <NUM>, and [(<NUM>-t-butoxyhexylmethylsilane-diyl)-bis (<NUM>-methyl-<NUM>-tert-butylphenylindenyl)]zirconium chloride represented by the Chemical Formula A of Comparative Preparation Example <NUM>, as transition metal compounds.

<NUM> of silica was weighed beforehand in a Shlenk flask, and then, <NUM> mmol of methylaluminoxane (MAO) was put, and they were reacted at <NUM> for <NUM> hours. After precipitation, the upper part was removed and the remaining part was washed with toluene one time. <NUM>µmol of the transition metal compound [(<NUM>-t-butoxyhexyl) (methyl)silane-diyl)-bis (<NUM>-methyl-<NUM>, <NUM>-benzoindenyl)]zirconium dichloride prepared in Comparative Example <NUM> was dissolved in toluene, and reacted at <NUM> for <NUM> hours. After the completion of the reaction, when precipitation was finished, the upper part solution was removed, and the remaining reaction product was washed with toluene one time. Subsequently, <NUM>µmol of the transition metal compound [(<NUM>-t-butoxyhexylmethylsilane-diyl)-bis (<NUM>-methyl-<NUM>-tert-butylphenylindenyl)]zirconium chloride prepared in Comparative Example <NUM> was dissolved in toluene, and then, additionally reacted at <NUM> for <NUM> hours.

After the completion of the reaction, when precipitation was finished, the upper part solution was removed, and the remaining reaction product was washed with toluene, washed with hexane again, and vacuum dried to obtain <NUM> of silica supported metallocene catalyst in the form of solid particles.

A supported catalyst was prepared by the same method as the step <NUM>) of Preparation Example <NUM>, using the transition metal compound represented by the following Chemical Formula C, [(dimethylsilane-diyl)-bis (<NUM>-methyl-<NUM>,<NUM>-benzoindenyl)]zirconium dichloride. <CHM>
<CHM>.

The bulk-slurry polymerization of propylene was progressed using continuous two loop reactors, in the presence of the silica supported metallocene catalysts according to Preparation Examples <NUM> and <NUM>.

Here, triethylaluminum (TEAL) and hydrogen gas were introduced respectively using a pump, and triethylaluminum (TEAL) and hydrogen gas were introduced in the contents described in the following Table <NUM>, based on the content of propylene continuously introduced. Further, for bulk-slurry polymerization, mud catalysts were used wherein <NUM> wt% of the supported catalysts prepared according to Preparation Examples <NUM> and <NUM> were mixed with oil, grease. The temperature of the reactor was <NUM>, and the reactor was driven such that production amount per hour became <NUM>.

Specific reaction conditions for the polymerization processes of Examples <NUM> and <NUM> are as shown in the following Table <NUM>, and through the polymerization process, homopolypropylene (homo mPP) resin of Example <NUM> was obtained.

A polymerization process was conducted by the same method as Example <NUM>, except that the metallocene single supported catalyst prepared in Comparative Preparation Example <NUM> was used instead of the supported catalyst of Preparation Example <NUM>, and the hydrogen input was changed to <NUM> ppm, thus obtaining homopolypropylene resin of Comparative Example <NUM>.

Homopolypropylene resin (Z/N homoPP, Manufacturing Company: LG Chem, Ltd. , H7700) prepared using a Ziegler-Natta catalyst was prepared.

A polymerization process was conducted by the same method as Example <NUM>, except that the hybrid supported catalyst prepared in Comparative Preparation Example <NUM> was used instead of the supported catalyst of Preparation Example <NUM>, thus obtaining homopolypropylene resin of Comparative Example <NUM>.

A polymerization process was conducted by the same method as Example <NUM>, except that the metallocene single supported catalyst prepared in Comparative Preparation Example <NUM> was used instead of the supported catalyst of Preparation Example <NUM>, thus obtaining homopolypropylene resin of Comparative Example <NUM>.

In the Table <NUM>, 'homomPP' designates homopolypropylene resin, and 'Z/N homoPP' designates homopolypropylene resin (commercial product) prepared using a Ziegler-Natta catalyst. Further, in the Table <NUM>, catalytic activity was calculated as the rate of the weight of produced polymer (kg PP) per gram (g) of used supported catalyst for unit hour (h). Particularly, in the case of Comparative Example <NUM>, since catalytic polymerization activity was remarkably lowered to <NUM>/g • cat, it may be difficult to commercially apply or process trouble may be generated.

Under the conditions described in the following Table <NUM>, batch type homopolymerization was conducted to obtain homopolypropylene resins of Comparative Examples <NUM> to <NUM>.

First, a <NUM> stainless reactor was vacuum dried at <NUM> and cooled, <NUM> of triethylaluminum was put at room temperature, and <NUM> of propylene was introduced. The mixture was stirred for <NUM> minutes, and <NUM> of the supported catalyst prepared in Comparative Example <NUM> was dispersed in <NUM> of hexane and prepared in the form of slurry, and introduced into the reactor using a nitrogen pressure. Here, <NUM> ppm of hydrogen gas was introduced together with the catalyst. Thereafter, the temperature of the reactor was slowly raised to <NUM>, and then, polymerization was conducted for <NUM> hour. After the completion of the reaction, unreacted propylene was vented.

A polymerization process was conducted by the same method as Comparative Example <NUM>, except that the polymerization temperature was changed to <NUM>, as shown in the following Table <NUM>, thus obtaining homopolypropylene resin of Comparative Example <NUM>.

A polymerization process was conducted by the same method as Comparative Example <NUM>, except that <NUM> of ethylene was introduced together with <NUM> of propylene to conduct random polymerization, as shown in the following Table <NUM>, thus obtaining polypropylene homo/random blend of Comparative Example <NUM>.

A polymerization process was conducted by the same method as Comparative Example <NUM>, except that the hydrogen gas input amount was changed to <NUM> ppm, as shown in the following Table <NUM>, thus obtaining homopolypropylene resin of Comparative Example <NUM>.

In the Table <NUM>, 'homomPP' designates homopolypropylene resin, and 'random mPP' designates polypropylene homo/random blend in which propylene and ethylene are randomly copolymerized.

For the polypropylene according to Examples and Comparative Examples, the propertie were evaluated as follows, and the results were shown in the following Table <NUM>.

Melt index was measured at <NUM> under <NUM> load according to ASTM D <NUM>, and expressed as the mass (g) of polymer that is molten and flows out for <NUM> minutes.

The tacticity (mol%) of polymer was measured through NMR (nuclear magnetic resonance) analysis.

Specifically, NMR spectrum was measured using a hexachlorobutadiene solution (based on tetramethylsilane), and tacticity (mol%) was calculated as a rate (%) of the area of the peaks appearing at <NUM> ppm to <NUM> ppm to the entire area (<NUM> %) of the peaks appearing at <NUM> ppm to <NUM> ppm.

The melting point (Tm) of polypropylene was measured using a Differential Scanning Calorimeter (DSC, device name: DSC <NUM>, manufacturing company: TA instrument). Specifically, polymer was heated to <NUM> and maintained at that temperature for <NUM> minutes, and then, the temperature was decreased to <NUM> and increased again, and the top of the DSC (Differential Scanning Calorimeter, manufactured by TA Instrument) curve was determined as a melting point. Here, the temperature increase and decrease rates were <NUM> /min, and as the melting point, the measurement result in the second temperature increase section was used.

Using GPC (gel permeation chromatography, manufactured by Water Company), the weight average molecular weight (Mw) and number average molecular weight (Mn) of the polymer were measured, and the weight average molecular weight was divided by the number average molecular weight to calculate molecular weight distribution (MWD).

Specifically, as gel permeation chromatography (GPC) device, Waters PL-GPC220 was used, and Polymer Laboratories PLgel MIX-B <NUM> length column was used. Here, the measurement temperature was <NUM>, <NUM>,<NUM>,<NUM>-trichlorobenzene was used as a solvent, and flow rate was set to <NUM>/min. Each polymer sample according to Examples and Comparative Examples was pretreated by dissolving in <NUM>,<NUM>,<NUM>-trichlocobenzene containing <NUM> % BHT at <NUM> for <NUM> hours, and prepared at the concentration of <NUM>/<NUM>, and then, fed in the amount of <NUM>µL, using GPC analysis equipment (PL-GP220). Mw and Mn were derived from a calibration curve formed using a polystyrene standard specimen. As the polystyrene standard specimen, <NUM> kinds having weight average molecular weight of <NUM>/mol, <NUM>/mol, <NUM>/mol, <NUM>/mol, <NUM>/mol, <NUM>/mol, <NUM>/mol, <NUM>/mol, <NUM>/mol were used.

For the polypropylene according to Examples and Comparative Exapmles, each sample was taken, <NUM> % strain was applied at <NUM>, and then, change in residual stress was measured for <NUM> minutes.

For the measurement of residual stress, Discovery Hybrid Rheometer (DHR) from TA Instruments was used, and the sample was sufficiently loaded between the upper and lower plates having diameters of <NUM> and dissolved at <NUM>, and then, a gap was fixed to <NUM> to measure.

Based on the measured residual stress data, residual stress rate (RS %) was calculated according to the following Calculation Formula <NUM>, and shown in the following Table <NUM>: <MAT>.

RS<NUM> is residual stress at <NUM> seconds (t<NUM>) after applying <NUM> % strain to the polypropylene resin sample, and
RS<NUM> is residual stress at <NUM> second (t<NUM>) after applying <NUM> % strain to the polypropylene resin sample.

As shown in the Table <NUM>, the homopolypropylene resins of Examples <NUM> and <NUM> have optimized melt index (MI) of <NUM>/<NUM> to <NUM>/<NUM> and tacticity of <NUM> % to <NUM> %, and simultaneously, have narrow molecular weight distribution (MWD) of <NUM> or less, low melting point (Tm) of <NUM> or less, and low residual stress rate of <NUM> % or less. On the contrary, it can be seen that Comparative Examples <NUM> to <NUM> fail to simultaneously fulfill optimized ranges of tacticity, molecular weight distribution (MWD), melt index (MI), metling point (Tm) and residual stress rate. Particularly, it can be seen that in the case of Comparative Example <NUM>, due to the low catalytic activity, melt index (MI) increases, molecular weight distribution increases to <NUM>, and residual stress rate also increases to <NUM> %.

Using the polypropylene according to Examples and Comparative Examples as raw material, a melt blowing process was conducted to prepare spunbond non-woven fabric.

Specifically, using a <NUM> twin-screw extruder, a masterbatch of the polypropylene according to Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM> and Exolit (trademakr) OP950 additive (<NUM> wt%) was prepared, and then, it was pelletized. Subsequently, the masterbarch pellet was extruded into an ultrafine fiber web by a process similar to that described in Document [<NPL>], except that the molten masterbatch resin composition was fed to a melt pump (<NUM> rpm), and then, fed to a melt blowing die of <NUM> width, having outlets (<NUM> outlets/cm) and outlet diameter of <NUM> µm, using a <NUM> Brabender conical type twin screw extruder.

The melting temperature was <NUM>, the screw speed was <NUM> rpm, the die was maintained at <NUM>, primary air temperature and pressure were respectively <NUM> and <NUM> kPa (<NUM> psi), polymer treatment speed was <NUM>/hr, and collector/die distance was <NUM>.

For the spunbond non-woven fabrics prepared using polypropylene resins according to Exapmles and Comparative Examples, the properties were evaluated as follows, and the results were shown in the following Table <NUM>.

The weight of non-woven fabric that was prepared by extruding into an ultrafine fiber web according to Experimental Example <NUM> was measured, and the weight of non-woven fabric per unit area was calculated.

When preparing non-woven fabric according to Experimental Example <NUM>, the processability of non-woven fabric was evaluated according to whether or not breakage was generated, and if breakage generation is <NUM> % or less, it was marked as "good", and if breakage generation is greater than <NUM> %, it was marked as "bad".

The strength of non-woven fabric was measured by <NUM> width cut strip method according to <NPL>).

The frictional coefficient of non-woven fabric was measured using a frictional coefficient measuring device (manufacturing company: Thwing-Albert Company, product name: FP-<NUM>).

The tactility of non-woven fabric was measured through the evaluation of <NUM> blind panels, and if <NUM> or more persons evaluate the non-woven fabric as being soft, it was judged as good and marked as "O", and if <NUM> to <NUM> persons evaluate so, judged as normal and marked as "△", and if <NUM> or less persons evaluate so, judged as bad and marked as "X".

As shown in the Table <NUM>, the homopolypropylene resins of Examples <NUM> and <NUM> with optimized tacticity, molecular weight distribution (MWD), melt index (MI), melting point (Tm), and residual stress rate do not generate breakage during a melt blowing process using it as raw material, thus enabling a continuous process, and decrease modulus, thus preparing non-woven fabric softer than the existing products.

Meanwhile, it was confirmed that the polypropylene resins of Comparative Examples <NUM> to <NUM> in which tacticity, molecular weight distribution (MWD), melt index (MI), melting point (Tm), and residual stress rate do not fall within the optimized ranges, generate breakage during a melt blowing process using it as raw material, and thus, continuous process cannot be conducted, and due to wide molecular weight distribution, strength is lowered, or due to high tacticity, frictional coefficient or tactility of prepared non-woven fabric is lowered.

Particularly, it was confirmed that in Comparative Example <NUM>, melting point increases, and frictional coefficient or tactility of prepared non-woven fabric is lowered. It was confirmed that in Comparative Examples <NUM> and <NUM>, due to wide molecular weight distribution of <NUM> or more, processability is lowered when preparing non-woven fabric, and the entire uniformity of non-woven fabric is lowered (partially sparse and dense parts exist), and thus, strength, frictional coefficient, and tactility are lowered. In Comparative Example <NUM>, since the resin has high melt index (MI), non-woven fabric could not be produced (not prepared), and thus, the properties of non-woven fabric could not be measured.

Claim 1:
A homopolypropylene resin for non-woven fabric, wherein the homopolypropylene resin has tacticity of <NUM> % to <NUM> %, molecular weight distribution of <NUM> or less, melt index of <NUM>/<NUM> to <NUM>/<NUM>, melting point of <NUM> or less, and residual stress rate of <NUM> % or less,
wherein the tacticity is measured through NMR analysis using a hexachlorobutadiene solution based on tetramethylsilane, and calculating the rate of the area of the peaks appearing at <NUM> ppm to <NUM> ppm to the entire area of the peaks appearing at <NUM> ppm to <NUM> ppm;
the molecular weight distribution is measured by measuring the weight average molecular weight (Mw) and number average molecular weight (Mn) of homopolypropylene resin, respectively, using gel permeation chromatography (GPC), and calculating the rate of the weight average molecular weight to the number average molecular weight (Mw/Mn);
wherein the melt index is measured measured at <NUM> under load of <NUM> according to ASTM D <NUM>;
the melting point is measured by increasing the temperature of the homopolypropylene resin to <NUM>, maintaining that temperature for <NUM> minutes, decreasing temperature to <NUM>, and then, increasing temperature again, and defining the top of the DSC curve as the melting point; and
the residual stress rate is a value measured according to the following Calculation Formula <NUM>: <MAT>
In the Calculation Formula <NUM>, RS<NUM> is residual stress at one time point (t<NUM>) of less than <NUM> seconds after applying <NUM> % strain to the homopolypropylene resin, and RS<NUM> is residual stress at one time point (t<NUM>) between <NUM> seconds to <NUM> seconds after applying <NUM> % strain to the homopolypropylene resin.