KR101485566B1 - Polyethylene having excellent sealing property at low temperature, and method for preparing the same - Google Patents

Abstract

The present invention relates to a polyethylene having excellent low-temperature and low-temperature sealing strength, a method for producing the polyethylene using the hybrid supported metallocene catalyst, and a film comprising the polyethylene. The polyethylene of the present invention has the following characteristics: 1) the density is 0.91 to 0.94 g / cm 3; 2) the index of Broad Orthogonal Comonomer Distribution (BOCD) is 0 to 3; and 3) the slope of the SCB distribution is the center (Weight-average molecular weight / number-average molecular weight) of 3 to 5 in the low molecular weight region, and 4) the molecular weight distribution (weight average molecular weight / number average molecular weight) . The polyethylene of the present invention has a melt flow rate ratio within a range suitable for processing, and is excellent in workability and moldability. In addition, the polyethylene has excellent low-temperature sealing performance and low-temperature sealing strength due to low heat sealing start temperature.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyethylene for a film having excellent low-temperature sealability, and a method for producing the polyethylene. [0002]

The present invention relates to a polyethylene having excellent low-temperature and low-temperature sealing strength, a method for producing the polyethylene using the hybrid supported metallocene catalyst, and a film comprising the polyethylene.

Linear low density polyethylene is widely used in stretch films and overlap films which are difficult to apply conventional low density polyethylene or high density polyethylene since they have high breaking strength and elongation as well as general polyethylene properties and excellent tear strength and falling impact strength.

The low-density polyethylene produced by the high-pressure method is used for films and hollow containers because of its high melt tension and good moldability. However, since the high-pressure-treated low-density polyethylene has a number of long-chain branched structures, there is a problem that mechanical strength such as tensile strength, tear strength or impact strength is inferior.

The ethylene polymer obtained by using the Ziegler catalyst is superior in mechanical strength such as tensile strength, tear strength or impact strength, but has a disadvantage that the molded article such as a film becomes sticky as compared with the high-pressure processed low density polyethylene.

To solve this problem, various ethylene polymers using a metallocene catalyst as a homogeneous catalyst (single site catalyst) are disclosed.

Japanese Patent Application Laid-Open No. 2005-97481 discloses an ethylene polymer obtained by gas phase polymerization in the presence of a catalyst comprising racemic-ethylene bis (1-indenyl) zirconium diphenoxide, and JP-A-1997-111208 (EXACT) obtained by using an ethylene-bis (4,5,6,7-tetrahydroindenyl) zirconium compound as a polymerization catalyst (Exxon Chemical Co., Ltd., EXACT) An ethylene polymer obtained by high pressure ion polymerization in the presence of a catalyst comprising dichloride and methyl alumoxane is disclosed in Japanese Patent Laid-Open No. 2002-3661 in which bis (n-butylcyclopentadienyl) zirconium dichloride and methyl alu Discloses an ethylene-based polymer obtained by using a catalyst comprising a polyvinyl alcohol and a polyvinyl alcohol.

U.S. Patent No. 6,180,736 discloses a method for producing polyethylene in which a single metallocene catalyst is used and produced in a single gas phase reactor or continuous slurry reactor, the production cost is low, fouling hardly occurs, and the polymerization activity is stable .

U.S. Patent No. 6,911,508 reports the preparation of improved rheology-modified polyethylenes using a new metallocene catalyst compound and polymerizing in a single gas phase reactor with 1-hexene as the comonomer. However, there is a problem that the workability is poor due to a narrow molecular weight distribution.

U.S. Patent No. 6,828,394 discloses a process for producing polyethylene which is excellent in processability using a mixture of a monomer having good comonomer binding property and a monomer having no comonomer binding property and is particularly suitable for a film.

In addition, U.S. Patent No. 6,841,631 and U.S. Patent No. 6,894,128 disclose that a polyethylene having at least two kinds of metal compounds is used as a metallocene-based catalyst and has a molecular weight distribution of at least two, and is used for films, blow molding, It is reported that it is applicable. However, these products have improved processability, but the dispersed state of the unit particles in molecular weight is not uniform, so that the extrusion appearance is rough and the physical properties are not stable even under relatively good extrusion conditions.

Against this backdrop, there is a continuing need to produce better products with a balance between physical and processability, and further improvements are needed.

The present invention aims to provide polyethylene having excellent low-temperature heat-sealability and low-temperature sealing strength as compared with conventionally known ethylene-based polymers, a process for producing the polyethylene, and a film containing the polyethylene.

The inventors of the present invention have found that an ethylene polymer having a specific range of density, a specific range of Biocydy index, and an S-seeding distribution slope of a specific type and having a molecular weight distribution in a specific range is excellent in low temperature heat sealing property and low temperature strength, The present invention has been completed.

In order to achieve the above object,

1) the density is 0.91 to 0.918 g / cm 3,

2) Broad Orthogonal Comonomer Distribution (BOCD) Index is 0 to 3,
3) In the SCB distribution curve, centering on the peak value (Mp) of the molecular weight distribution curve,
In the high molecular weight region defined on the right side of the center, there exists a section having a slope of the S / S distribution curve that is three times or more larger than the slope of the S / S distribution curve in the low molecular weight region defined as the left side of the center,

4) The molecular weight distribution (weight average molecular weight / number average molecular weight) is 3 to 5

≪ / RTI >

The present invention also provides a method for producing the polyethylene using a hybrid supported metallocene catalyst in which at least two different metallocene compounds are supported on one support.

The present invention also provides a film comprising the polyethylene.

The polyethylene of the present invention has a melt flow rate ratio within a range suitable for processing, and is excellent in workability and moldability. In addition, the polyethylene has excellent low-temperature sealing performance and low-temperature sealing strength due to low heat sealing start temperature.

1 is a graph showing the GPC-FTIR result and BOCD index of Sample A. FIG.
2 is a graph showing the GPC-FTIR result and the BOCD index of the sample B. Fig.
3 is a graph showing molecular weight distributions of the polymers prepared according to Examples and Comparative Examples of the present invention.
As shown in FIG. 3, the product according to the present invention has a structure in which the molecular weight distribution is broader than that of the conventional product, and the molecular weight distribution appears in the low molecular weight portion.
4 is a graph showing the heat sealing start temperature and the low temperature sealing strength of a polymer produced according to Examples and Comparative Examples of the present invention. Hot tack was processed under the conditions of a pressure of 1 kg and a sealing time of 0.5 sec, And FIG.
5 is a graph showing the GPC-FTIR results and BOCD index of the polymer prepared according to an embodiment of the present invention.
6 is a graph showing GPC-FTIR results and BOCD indexes of existing products of the company itself and other companies.

Hereinafter, the present invention will be described in detail.

The first aspect of the present invention is as follows: 1) the density is 0.91 to 0.918 g / cm 3; 2) the Broad Orthogonal Comonomer Distribution (BOCD) index is 0 to 3; and 3) the SCB distribution curve , And the peak value (Mp) of the molecular weight distribution curve as the center,
In the high molecular weight region defined on the right side of the center, there exists a section having a slope of the S / S distribution curve that is three times or more larger than the slope of the S / S distribution curve in the low molecular weight region defined as the left side of the center,
4) A polyethylene having a molecular weight distribution (weight average molecular weight / number average molecular weight) of 3 to 5 is provided.

The density is preferably 0.91 to 0.94 g / cm3, more preferably 0.915 to 0.925 g / cm3. When the density is not less than 0.91 g / cm 3, the resulting ethylene polymer has good dropout impact strength, and when the density is not more than 0.94 g / cm 3, the resulting ethylene polymer has good low-temperature sealing properties.

The polyethylene according to the present invention is preferably a copolymer of ethylene and an alpha-olefin comonomer, which is an olefinic monomer. The density depends on the alpha-olefin content of the ethylene polymer. The lower the alpha-olefin content, , The higher the alpha-olefin content, the lower the density. It is also known that the alpha-olefin content in the ethylene polymer is determined by the composition ratio of alpha-olefin to ethylene (alpha-olefin / ethylene) in the polymerization system (see, for example, Walter Kaminsky, Makromol. 606 (1992)). For this reason, it is possible to produce an ethylene polymer having an upper limit to a lower limit of the density requirement of the present invention by increasing or decreasing alpha-olefin / ethylene.

As the alpha-olefin-based comonomer, an alpha-olefin having 4 or more carbon atoms may be used. Examples of alpha-olefins having 4 or more carbon atoms include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, , 1-octadecene, 1-eicosene, and the like, but are not limited thereto. Of these, alpha-olefins having 4 to 10 carbon atoms are preferable, and one or more alpha-olefins may be used together as comonomers.

In the copolymer of the ethylene and the alpha-olefin-based comonomer, the content of ethylene is preferably 55 to 99.9% by weight, and most preferably 90 to 99.9% by weight. The content of the alpha-olefin-based comonomer is preferably 0.1 to 45% by weight, and most preferably 0.1 to 10% by weight.

In the term " BOCD Index " used herein, the term " BOCD " is a newly developed concept of a polymer structure related term. The BOCD structure is a new structure in which the content of comonomers such as alpha-olefins is concentrated in the high molecular weight main chain, ie, the content of short chain branching (SCB) increases toward higher molecular weight. do. Herein, the term short chain branch (SCB) means branches having 2 to 6 carbon atoms attached to the main chain. Usually, comonomers such as 1-butene, 1-hexene and 1-octene, It means side branches made when olefin is used.

The molecular weight, molecular weight distribution and SCB content can be measured simultaneously and continuously using GPC-FTIR equipment. The BIO-CID index calculates the SCB content (unit: 1,000C) in the range of 30% (total 60%) left and right of the molecular weight distribution (MWD) based on the weight average molecular weight (Mw) .

[Equation 1]

If the BiocDi index is 0 or less, it is not a Biocyte structure polymer. If it is larger than 0, it can be regarded as a Biocyte structure polymer. If the Biocyte index is larger, the BiocyDi characteristic is superior.

For example, when measuring GPC-FTIR of samples A and B having different polymer structures, results as shown in FIGS. 1 and 2 can be obtained. Here, sample A has a bio-CD index of -0.26, It is not a polymer, and sample B has a bio-CD index of 1.48 and can be interpreted as a polymer having an excellent bio-CD structure.

A polymer having a biocide structure has properties that make it have better physical properties by concentrating tie molecules such as ssibee in a high molecular weight portion which has a relatively higher physical property than a low molecular weight substance. This is a characteristic of our metallocene products that are differentiated from other competitors' products and has a great influence on complementing all mechanical properties. In the present invention, a high-temperature sealing strength of the product is improved by concentrating the high-molecular-weight fraction in the high-molecular-weight portion and implementing a small amount of the low-molecular-weight fraction in the low molecular weight portion through the catalyst technology.

Here, the low-temperature sealing strength refers to the force required to separate a sealed surface when a hot tack is pressed under a predetermined condition.

In the polyethylene according to the present invention, the peak value (Mp) of the molecular weight distribution curve is centered on the SCB distribution curve,
In the high molecular weight region defined on the right side of the center, there exists a section having a slope of the S / S distribution curve that is three times or more larger than the slope of the S / S distribution curve in the low molecular weight region defined as the left side of the center .

The slope of the S / C distribution varies depending on the characteristics of the catalyst. In the case of conventional products and conventional metallocene catalyst-based products, the product has a structure as shown in FIG. 6, but the product exhibits a low temperature sealing property and a low temperature sealing strength In order to improve the low molecular weight polyethylene production catalyst and the high molecular weight polyethylene production catalyst, a product having a bio-CD structure as shown in FIG. 5 was developed.

The polyethylene of the present invention has a molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of 3 to 5 as measured by GPC.

When the molecular weight distribution is 3 or more, the obtained ethylene polymer has good moldability, and when the molecular weight distribution is 5 or less, the obtained ethylene polymer has good impact strength.

In addition, the melt flow index (190 ° C under 2.16 kg load conditions) of the polyethylene according to the present invention is preferably 0.05 to 2 g / 10 min, more preferably 0.1 to 1 g / 10 min. When the melt flow index is in the above range, it is preferable as an optimum point that can harmonize the molding processability and the mechanical properties.

The value of the melt flow rate ratio (MFRR) of the polyethylene of the present invention is preferably 5 to 20 in terms of appearance, workability, and physical properties.
The polyethylene of the present invention may have a heat sealing initiation temperature of 90 to 94 占 폚 (1 kg, 0.5 sec), a low temperature sealing strength of 0.03 kgf (1 kg, 0.5 sec, 100 占 폚) (1 kg, 0.5 sec) and the low-temperature sealing strength may be 0.2 kgf (1 kg, 0.5 sec, 105 ° C) or higher.

Also, it is preferable that the polyethylene of the present invention has 1 to 20 SCBs per 1,000 carbon atoms of polyethylene.

The weight average molecular weight of the polyethylene according to the present invention is preferably 80,000 to 300,000, but is not limited thereto.

The polyethylene according to the present invention may contain other additives. Specifically, such additives include heat stabilizers, antioxidants, UV absorbers, light stabilizers, metal deactivators, fillers, reinforcing agents, plasticizers, lubricants, emulsifiers, pigments, optical bleaches, flame retardants, antistatic agents and foaming agents. The kind of the additive is not particularly limited, and general additives known in the art can be used.

The polyethylene according to the present invention is excellent in processability, has a melt flow ratio (MFRR) value in a range suitable for processing, and is excellent in moldability, tensile strength, tear strength, It can be used for production.

The second aspect of the present invention provides a method for producing polyethylene using a hybrid supported metallocene catalyst in which at least two different metallocene compounds are supported on one support. The polyethylene according to the present invention can be produced, for example, according to the production method described below, but is not limited thereto.

According to the method for producing polyethylene of the present invention, there is provided a process for producing polyethylene having a molecular weight distribution curve of at least two in the presence of a mixed supported metallocene catalyst having at least two different metallocene compounds carried on one carrier .

In the method for preparing polyethylene according to the present invention, silica, silica-alumina, silica-magnesia, etc., dried at a high temperature may be used as a carrier which can be used for preparing the hybrid supported metallocene catalyst, ₂ O, K ₂ CO ₃ , BaSO ₄ , Mg (NO ₃ ) ₂ and the like, carbonate, sulfate, and nitrate components.

The smaller the amount of hydroxyl groups (-OH) on the surface of the support is, the more difficult it is to remove all the hydroxyl groups (-OH). Therefore, the amount of hydroxyl group (-OH) is preferably 0.1 to 10 mmol / g, more preferably 0.1 to 1 mmol / g, and most preferably 0.1 to 0.5 mmol / g. The amount of the surface hydroxyl group (-OH) can be controlled by the production conditions or the method of the carrier, or the drying conditions or the method (temperature, time, pressure, etc.). Further, in order to reduce side reactions caused by some hydroxyl groups remaining after drying, it is also possible to use a carrier in which the hydroxyl group (-OH) is chemically removed while preserving the highly reactive siloxane groups participating in the loading.

In the method for producing polyethylene according to the present invention, the mixed supported metallocene catalyst is a mixed supported metallocene catalyst in which at least two different metallocene compounds are supported on one support, and among the metallocene compounds The first metallocene compound may be represented by the following general formula (1), and the second metallocene compound which is another one of the metallocene compounds may be represented by the following general formula (2).

[Chemical Formula 1]

(L ¹ ) _p (L ² ) MQ _{3 -p}

In Formula 1, M is a Group 4 transition metal of the periodic table,

L ¹ and L ² are the same or different and each is independently a hydrogen radical, a C _{1 ~ 20} 14 is substituted by an alkyl radical, a hydrocarbyl radical of a C _{2 ~ 20} alkenyl radicals, C _{6 ~ 30} aryl radicals, C _{7 ~ 30} alkylaryl radical, C _{7 ~ 30} arylalkyl radicals, C _{1 ~ 20} of the Or a ligand in which two adjacent carbon atoms are connected by a hydrocarbyl radical to form a 4- to 8-membered ring,

Q is a halogen radical, C _{1 ~ 20} An alkyl radical, alkenyl radical, an arylalkyl radical of C _{6 ~ 30} aryl radicals, C _{7 ~ 30} alkylaryl radicals or C _{7 ~ 30} of the C _{2 ~ 20,} the same as or different from each other, if more than one Q and , Two Q's may together form a hydrocarbon ring,

p is 1 or 0,

(2)

In Formula 2,

M is a Group 4 transition metal of the periodic table;

R ³ are the same or different and each independently represents an aryl radical of C _{1 ~ 20} alkyl radicals, C _{2 ~ 20} alkenyl radicals, C _{3 ~ 30} cycloalkyl radicals, C _{6 ~ 30} of each other, C _{7 ~ 30} alkyl aryl radicals, C _{7 ~ 30} aryl-alkyl radical, or a C _{8 ~ 30} arylalkyl radical;

Q and Q 'are the same or different and are each independently a halogen radical, a C _{1 ~ 20} alkyl radical, an alkylaryl radical of C _{2 ~ 20} alkenyl radicals, C _{6 ~ 30} aryl radicals, C _{7 ~ 30} of the , Or an arylalkyl radical of C _{7 to 30} , and Q and Q 'together may form a C _{1 to} C ₂₀ hydrocarbon ring;

B is a C _{1 ~ 4} alkylene radical, dialkyl silicon, germanium, alkyl phosphine, or amine, with two cyclopentadienyl based ligands, or a cyclopentadienyl ligand and JR ⁴ share sequence _{Z -Y} bond It is a bridge that binds by;

R ⁴ is a hydrogen radical, an aryl radical of C _{1 ~ 20} alkyl radicals, C _{2 ~ 20} alkenyl radicals, C _{6 ~ 30} aryl radicals, C _{7 ~ 30} alkylaryl radicals or C _{7 ~ 30} of the of the a ;

J is a Group 15 element or a Group 16 element of the periodic table;

z is the oxidation number of the element J;

y is the combined number of J elements;

n and n 'are the same as or different from each other, and each independently represents a positive integer of 0 or more;

r is an integer from 0 to 2;

Y represents a heteroatom of O, S, N or P;

A represents an alkyl radical of hydrogen or C _{1 ~ 10.}

In the method for producing polyethylene according to the present invention, the mixed supported metallocene

A) contacting the supported metallocene catalyst supported on at least one metallocene compound with a cocatalyst to form an activated supported metallocene catalyst; And b) further carrying one or more metallocene compounds different from the metallocene compound on the activated supported metallocene catalyst.

For example, one metallocene compound that induces a low molecular weight polyethylene and one metallocene compound that induces a high molecular weight polyethylene are impregnated in a single carrier together with the co-catalyst, and the reaction in a single reactor It is possible to prepare a hybrid supported metallocene catalyst which can easily control the molecular weight distribution.

In the method for producing polyethylene according to the present invention, the co-catalyst contains a Group 13 metal of the periodic table, and the molar ratio of Group 13 metal / Group 4 metal of the mixed supported metallocene catalyst is preferably 1 to 10,000, To 1,000 is more preferable, and 10 to 100 is most preferable.

Representative co-catalysts that can be used to activate the metallocene compound include alkylaluminum-based trimethylaluminum, triethylaluminum, triisobutylaluminum, trioctylaluminum, methylaluminoxane, ethylaluminoxane, isobutylaluminoxane , Butylaluminoxane and the like. Examples of the neutral or ionic compound of the boron system include tripentafluorophenylboron, tributylammonium tetrapentafluorophenylboron and the like, but the present invention is not limited thereto.

The content of the Group 4 transition metal in the hybrid supported metallocene catalyst finally produced in the present invention is preferably 0.1 to 20% by weight, more preferably 0.1 to 10% by weight, and more preferably 1 to 3% by weight, Is most preferable. When the content of the Group 4 transition metal of the Periodic Table of Elements exceeds 20% by weight, the catalyst may escape from the carrier during ethylene polymerization to cause problems such as fouling, and the production cost is increased.

The molar ratio of Group 13 metal / Group 4 metal of the periodic table in the mixed supported metallocene catalyst is preferably 1 to 10,000, more preferably 1 to 1,000, 100 is most preferable.

It is preferable that the loading of the second metallocene compound is carried in a molar ratio of 0.5 to 2 based on 1 mole of the first metallocene compound to variously control the molecular weight distribution of the final polyethylene.

The amount of the promoter to be supported is preferably in the range of 1 to 10,000 moles per 1 mole of the metal contained in the first and second metallocene compounds, based on the metal contained in the co-catalyst.

The hybrid supported metallocene catalyst itself can be used for ethylene polymerization and may be used for prepolymerization in contact with olefinic monomers such as propylene, 1-butene, 1-hexene, 1-octene and the like.

The hybrid supported metallocene catalyst of the present invention is an aliphatic hydrocarbon solvent having 5 to 12 carbon atoms such as isobutane, pentane, hexane, heptane, nonane, decane and isomers thereof; Aromatic hydrocarbon solvents such as toluene and benzene; Dichloromethane, and a hydrocarbon solvent substituted with a chlorine atom such as chlorobenzene. Preferably, the solvent is treated with a small amount of aluminum to remove a small amount of water, air, or the like acting as a catalyst poison.

A polyethylene copolymer having a molecular weight distribution curve having a molecular weight distribution of at least two can be prepared using the hybrid supported metallocene catalyst. Copolymerization with alpha-olefins using a hybrid supported metallocene catalyst is particularly advantageous when the alpha-olefin comonomer is derived by a second metallocene compound, which produces a high molecular weight fraction, resulting in a high performance polyethylene Thereby making it possible to prepare a copolymer.

The preparation of the polyethylene can be carried out in one continuous slurry polymerization reactor, a loop slurry reactor, a gas phase reactor or a solution reactor, and can be carried out according to a conventional method, continuously feeding ethylene and comonomer with alpha-olefin having 4 or more carbon atoms, Can be performed.

The polymerization temperature at the time of copolymerizing ethylene and a high alpha-olefin having 4 or more carbon atoms as a comonomer by using the hybrid supported metallocene catalyst of the present invention is preferably 25 to 500 DEG C, more preferably 25 to 200 DEG C, More preferably 50 to 150 ° C. The polymerization pressure is preferably 1 to 100 Kgf / cm2, more preferably 1 to 50 Kgf / cm2, and most preferably 5 to 30 Kgf / cm2.

The polyethylene copolymer according to the present invention can be obtained by copolymerization of ethylene with an alpha-olefin having 4 or more carbon atoms using the hybrid supported metallocene compound as a catalyst, and may have a molecular weight distribution or an equivalent molecular weight distribution.

In a third aspect of the present invention, the present invention provides a film comprising the polyethylene. The film according to the present invention is manufactured by a method of inflating a pellet of a polyethylene copolymer into a single-screw extruder so as to have a thickness of about 0.05 mm, as is well known in the art, but is not limited thereto.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the examples are for illustrating the present invention, and the present invention is not limited thereto.

Manufacturing example  - Metallocene  Preparation of Catalyst

Organic reagents and solvents required for catalyst preparation and polymerization were purified by standard methods from Aldrich and ethylene was polymerized after passing a high purity product from Applied Gas Technology through water and oxygen filtration apparatus , The contact between air and water was blocked at all stages of catalyst synthesis, support and polymerization, and the reproducibility of the experiment was improved.

[Production of first metallocene catalyst - (CH ₃ ) (CH ₂ ) ₃ -C ₅ H ₄ ] ₂ ZrCl ₂ ]

n-Butyl chloride was reacted with NaCp to obtain n-BuCp. Thereafter, n-BuCp was dissolved in THF at -78 ° C, n-butyllithium (n-BuLi) was added slowly, and the temperature was further raised to room temperature, followed by reaction for 8 hours. The lithium salt solution thus prepared was slowly added to a suspension solution of ZrCl ₄ (THF) ₂ (1.70 g, 4.50 mmol) / THF (30 ml) at -78 ° C. and further reacted at room temperature for 6 hours. All volatile materials were vacuum dried, and hexane solvent was added to the obtained oily liquid substance to be filtered. The filtered solution was vacuum dried, and hexane was added thereto to induce a precipitate at a low temperature (-20 ° C). The obtained precipitate was filtered off at a low temperature to obtain a (CH ₃ ) (CH ₂ ) ₃ -C ₅ H ₄ ] ₂ ZrCl ₂ compound in the form of a white solid. (Yield 50%)

[Production of second metallocene catalyst - Synthesis of methyl (6-t-butoxyhexyl) silyl (? ⁵ -tetramethyl Cp) (t-butylamido)] titanium dichloride compound]

At room temperature, 50 g of Mg (s) was added to the 10 L reactor and THF 300 mL was added. About 0.5 g of I ₂ was added, and the reactor temperature was maintained at 50 ° C. After the reactor temperature stabilized, 250 g of 6-t-butoxyhexyl chloride was added to the reactor at a rate of 5 mL / min using a feed pump. The addition of 6-t-butoxyhexyl chloride increased the reactor temperature by 4 ~ 5 ℃. The mixture was stirred for 12 hours while continuously adding 6-t-butoxyhexyl chloride. After 12 hours of reaction, a black reaction solution was obtained. 2 mL of the resulting black solution was added, and water was added thereto. An organic layer was obtained, and 6-t-butoxyhexane was confirmed by 1 H-NMR, and Gringanrd reaction was carried out from 6-t-butoxyhexane I could see that it was going on. Thus, 6-t-butoxyhexylmagnesium chloride was synthesized.

500 g of MeSiCl ₃ and 1 L of THF were added to the reactor and the reactor temperature was cooled to -20 ° C. 560 g of synthesized 6-t-butoxyhexylmagnesium chloride was added to the reactor at a rate of 5 mL / min using a feed pump. After the supply of the Grignard reagent was completed, the reactor temperature was slowly raised to room temperature and stirred for 12 hours. After 12 hours of reaction, it was confirmed that MgCl ₂ salt of white was formed. 4 L of hexane was added to remove the salt through labdori to obtain a filter solution. The obtained filter solution was added to the reactor, and hexane was removed at 70 ° C to obtain a pale yellow liquid. The obtained liquid was confirmed to be the desired methyl (6-t-butoxyhexyl) dichlorosilane compound by 1 H-NMR.

_{1H-NMR (CDCl 3):} d = 3.3 (t, 2H), 1.5 (m, 3H), 1.3 (m, 5H), 1.2 (s, 9H), 1.1 (m, 2H), 0.7 (s, 3H )

After 1.2 mol (150 g) of tetramethylcyclopentadiene and 2.4 L of THF were added to the reactor, the reactor temperature was cooled to -20 占 폚. 480 mL of n-BuLi was added to the reactor at a rate of 5 mL / min using a feed pump. After the addition of n-BuLi, the reactor temperature was slowly raised to room temperature and stirred for 12 hours. After 12 hours of reaction, an equivalent amount of methyl (6-t-butoxyhexyl) dichlorosilane (326 g, 350 mL) was rapidly added to the reactor. After the reactor temperature was slowly raised to room temperature, the mixture was stirred for 12 hours. After the reactor was cooled to 0 ° C, 2 equivalents of t-BuNH ₂ were added. The reactor temperature was slowly raised to room temperature and stirred for 12 hours. After 12 hours of reaction, THF was removed and 4 L of hexane was added to obtain a filter solution from which salt was removed through labdori. The filter solution was added to the reactor again, and hexane was removed at 70 ° C to obtain a yellow solution. The resulting yellow solution was confirmed to be methyl (6-t-butoxyhexyl) (tetramethyl CpH) t-butylaminosilane compound by 1 H-NMR.

TiCl ₃ (THF) ₃ (10 mmol) was rapidly added to the dilithium salt of the ligand synthesized in n-BuLi and ligand dimethyl (tetramethyl CpH) t-butylaminosilane in THF solution. The reaction solution was agitated for 12 hours while slowly raising the temperature to -78 ° C. After stirring for 12 hours, an equivalent amount of PbCl ₂ (10 mmol) was added to the reaction solution at room temperature, followed by stirring for 12 hours. After stirring for 12 hours, a dark black solution with a blue color was obtained. THF was removed from the resulting reaction solution, and hexane was added to filter the product. After removal of hexane from the obtained filter solution, it was confirmed from the result of 1H-NMR that this compound was the desired [methyl (6-t-butoxyhexyl) silyl (η ⁵ -tetramethyl Cp) (t-butylamido)] TiCl ₂ compound.

_{1H-NMR (CDCl 3):} d = 3.3 (s, 4H), 2.2 (s, 6H), 2.1 (s, 6H), 1.8 ~ 0.8 (m), 1.4 (s, 9H), 1.2 (s, 9H ), 0.7 (s, 3H)

[Preparation of supported metallocene catalyst]

Silica (SYLOPOL 948, Grace Davison) was dehydrated under vacuum at a temperature of 400 ° C for 15 hours.

1.0 kg of the silica is put into a reactor, and 10 L of toluene is added thereto. 5 L of 10 wt% methylaluminoxane (MAO) / toluene solution was added, and the mixture was slowly reacted at 40 ° C with stirring. Thereafter, the reaction product was washed with a sufficient amount of toluene to remove the unreacted aluminum compound, and the remaining toluene was removed by reducing the pressure at 50 캜. After adding 10 L of toluene again, 80 g of the metallocene catalyst B synthesized in Preparation Example 1 was dissolved in toluene, and the mixture was reacted for 1 hour. After the reaction is completed, stirring is stopped, the toluene is separated by layer, and then washed once with 20 L of toluene solution. Thereafter, 20 g of the metallocene catalyst A synthesized in Production Example 2 was dissolved in toluene, and the mixture was added again and reacted for 1 hour. Thereafter, the solution was removed by filtration, washed twice with toluene, and dried under reduced pressure to obtain a solid powder.

Example

The supported metallocene catalyst obtained in the above Production Example was fed into a single loop slurry polymerization process to prepare a linear low density polyethylene according to a conventional method. As the comonomer, 1-hexene was used. The obtained polyethylene copolymer was granulated at an extrusion temperature of 180 to 210 ° C using a twin-screw extruder (75 psi, L / D = 36) after prescription of an antioxidant (Iganox 1010 + Igafos 168, CIBA) .

Comparative Example  One

The metallocene catalyst was fed into a single loop slurry polymerization process to produce linear low density polyethylene according to the method. As the comonomer, 1-hexene was used. The granulation and film forming of the obtained polyethylene were performed in the same manner as in Example 1, and the evaluation results of the properties are shown in Table 1.

Comparative Example  2

The metallocene catalyst was fed into a continuous two - stage slurry polymerization process to produce linear low density polyethylene according to a conventional method. As the comonomer, 1-hexene was used. The granulation and film forming of the obtained polyethylene were performed in the same manner as in Example 1, and the evaluation results of the properties are shown in Table 1.

Comparative Example  3

The metallocene catalyst was mixed at the upstream side of the reactor and then fed into a single gas phase polymerization process to prepare polyethylene according to a conventional method. As the comonomer, 1-hexene was used. The granulation and film forming of the obtained polyethylene were performed in the same manner as in Example 1, and the evaluation results of the properties are shown in Table 1.

Experimental Example  - Polyethylene property test

The polyethylene copolymer thus prepared was evaluated by the following method. The results are shown in Table 1, and Figs. 1 to 3.

[ Assessment Methods ]

1) Density: ASTM 1505

2) Melt Index (MI, 2.16 kg / 10 kg): Measuring temperature 190 占 폚, ASTM 1238

3) MFRR (MFR ₁₀ / MFR ₂ ): MFR _{10 The} ratio of the melt index (MI, 10 kg load) divided by MFR ₂ (MI, 2.16 kg load).

4) Molecular weight, molecular weight distribution: Number-average molecular weight, weight-average molecular weight and Z-average molecular weight were measured using Gel Permeation Chromatography-FT-IR (GPC-FTIR) at a measurement temperature of 160 ° C. The molecular weight distribution is represented by the ratio of the weight average molecular weight to the number average molecular weight.

5) BOCD Index: The SCB content in the range of 30% (total 60%) of the molecular weight distribution (MWD) based on the weight average molecular weight (Mw) in the analysis of the GPC- / 1,000 < 0 > C) was measured and a BIODY index was calculated by the following formula (1).

 [Equation 1]

Item Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Catalyst used Metallocene Metallocene Metallocene Metallocene Polymerization process Loop slurry Loop slurry Loop slurry weather Comonomer 1-hexene 1-hexene 1-hexene 1-hexene Density (g / cm ³⁾ 0.918 0.918 0.918 0.918 MI (2.16 kg) 1.0 1.0 1.0 1.0 MFRR (MFR ₁₀ / MFR ₂ ) 8.7 7.5 7.1 6.0 Molecular weight distribution (Mw / Mn) 3.8 2.9 2.8 2.5 BOCD Index 0.65 1.34 -0.26 0.10 [Film properties and workability] Tensile strength (kg / cm ² ) MD 550 575 535 570 TD 525 525 505 535 Elongation (%) MD 600 615 630 615 TD 700 735 750 745 Tear strength (g / 탆) MD 13 16 13 11 TD 17 17 15 15 Fallen impact strength (g) 850 1210 835 1100 Haze 20 15 10 22 [Low temperature sealing property and low temperature sealing strength] Heat seal initiation temperature
[1 kg, 0.5 sec] 92 97 95 95 Low temperature sealing strength (kgf)
[1 kg, 0.5 sec, 100 캜] 0.04 0.01 0.01 0.01 Low temperature sealing strength (kgf)
[1 kg, 0.5 sec, 105 캜] 0.27 0.08 0.12 0.02

As can be seen from the above Table 1, the polyethylene copolymer obtained in the Examples has a molecular weight distribution with a high molecular weight distribution structure using a hybrid supported metallocene catalyst, Based on the structure, it was confirmed that the low - temperature and low - temperature sealing strengths were better by controlling the distribution of the low - molecular weight fraction and the high molecular weight fraction.

Claims (20)

1) the density is 0.91 to 0.918 g / cm 3,
2) Broad Orthogonal Comonomer Distribution (BOCD) Index is 0 to 3,
3) In the SCB distribution curve, centering on the peak value (Mp) of the molecular weight distribution curve,
In the high molecular weight region defined on the right side of the center, there exists a section having a slope of the S / S distribution curve that is three times or more larger than the slope of the S / S distribution curve in the low molecular weight region defined as the left side of the center,
4) The molecular weight distribution (weight average molecular weight / number average molecular weight) is 3 to 5,
5) The melt flow rate ratio (MFRR) value is 7 to 20,
6) The heat seal initiation temperature was 90 to 94 占 폚 (1 kg, 0.5 sec)
7) A film comprising polyethylene, wherein the low temperature sealing strength is at least 0.03 kgf (1 kg, 0.5 sec, 100 캜). delete The method according to claim 1,
The polyethylene had a heat seal initiation temperature of 90 to 94 占 폚 (1 kg, 0.5 sec)
The low-temperature sealing strength is 0.2 kgf (1 kg, 0.5 sec, 105 ° C) or more
Lt; / RTI > The film according to claim 1, wherein the polyethylene has a melt flow index (190 ° C, 2.16 kg load condition) of 0.05 to 2 g / 10 min. delete The film according to claim 1, wherein the short chain branching (SCB) content per 1,000 carbons of the polyethylene is 1 to 20. The film of claim 1, wherein the polyethylene is a copolymer of ethylene and an alpha-olefinic comonomer. delete [Claim 7] The composition of claim 7, wherein the alpha-olefin comonomer is selected from the group consisting of 1-butene, 1-pentene, 1-hexene, , 1-hexadecene, 1-octadecene, and 1-eicosene. The film according to claim 1, wherein the weight average molecular weight of the polyethylene is 80,000 to 300,000. delete delete delete delete delete delete delete delete delete delete

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