WO2001046276A1

WO2001046276A1 - Metallocene catalysts having multi-nuclear constrained geometry and ethylene/aromatic vinyl compound co-polymers prepared by using the same

Info

Publication number: WO2001046276A1
Application number: PCT/KR2000/001486
Authority: WO
Inventors: Sung Cheol Yoon; Xuequan Zhang; Jae Gon Lim; Hyun Joon Kim; Young Sub Lee
Original assignee: Samsung General Chemicals Co., Ltd.
Priority date: 1999-12-20
Filing date: 2000-12-18
Publication date: 2001-06-28
Also published as: KR20010057201A; AU2031101A; KR100371909B1

Abstract

The metallocene catalyst according to the present invention contains in one molecule 2 to 4 transition metals that are bonded with ligands. The metallocene catalyst is used for preparing an ethylene/vinyl aromatic compound copolymer. The metallocene catalyst is employed with a cocatalyst such as organometallic compound or amixture of non-coordinated Lewis acid and alkyl aluminum. The ethylene/vinyl aromatic compound copolymer prepared by using the metallocene catalyst shows an isotacticity of at least 60%, and especially an alternating index of at least 80% measured by 13C NMR analysis.

Description

METALLOCENE CATALYSTS HAVING MULTI-NUCLEAR

CONSTRAINED GEOMETRY AND ETHYLENE/AROMATIC VINYL

COMPOUND CO POLYMERS PREPARED BY USING THE SAME

Field of the Invention

The present mvention relates to metaUocene catalysts for copolymerization of ethylene/vinyl aromatic compound. More particularly, the present invention relates to the constrained geometry metaUocene catalysts having a structure linked with more than two ligands of transition metal complex, isotactic-alternating- ethylene/vinyl aromatic compound copolymers having high isotacticity, alternating index and improved physical properties, which are copolymerized using said catalysts, and a method of preparing the copolymers.

Background of the Invention

In general, olefm or styrene polymers are prepared by radical polymerization, ion polymerization, or coordination polymerization using Ziegler-Natta Catalysts. By radical polymerization or ion polymerization, atactic polymers are obtained and by coordination polymerization using a Ziegler-Natta Catalyst, isotactic polymers are mainly obtained. The polymers are classified into an atactic, an isotactic and a syndiotactic structure depending on the position of benzene rings as side chains. An atactic structure has an irregular arrangement of the benzene rings and an isotactic polystyrene has an arrangement that the benzene rings are positioned at one side of the polymer main chain. On the other hand, a syndiotactic structure has a regularly alternating arrangement of the benzene rings.

Copolymerization of ethylene and a vinyl aromatic compound such as styrene has been studied for a couple of decades. At the beginning of time, a polymerization method using a heterogeneous Ziegler-Natta catalyst was introduced (Polymer Bulletin 20, 237-241 (1988)). However, the conventional method has shortcomings in that the catalyst has poor activity, the copolymer has a low content of styrene and poor uniformity, and the copolymer is mostly a homopolymer. Further, a copolymer of ethylene and styrene has been prepared using a homogeneous Ziegler-Natta catalyst system comprising a transition metal compound and an organoaluminum compound.

Japanese Patent Laid-Open Nos. 3-163088 and 7-53618 disclose a pseudo-random styrene/ethylene copolymer prepared by using a catalyst with a constrained geometrical structure, which does not have any head-to-tail bonds. The phenyl groups in the alternating structure of the pseudo-random styrene/ethylene copolymer do not have stereoregularity. When the larger amount of styrene was incoφorated in the pseudo-random styrene/ethylene copolymer, the copolymer shows the same properties as an amoφhous resin with no crystallinity.

Japanese Patent Laid-Open No. 6-49132 and Polymer Preprints (Japan 42, 2292 (1993)) disclose a method for producing a styrene/ethylene copolymer which is a pseudo random copolymer with no head-to-tail bonds. The styrene/ethylene copolymer is prepared a bridged indenyl zirconium complex and a cocatalyst. According to the Polymer Preprints, the ethylene/styrene alternating structure in the pseudo random copolymer does not show stereoregularity. Further, Japanese Patent Laid-Open No.3-250007 and Stud. Surf. Sci. Catal.

517 (1990) disclose a styrene/ethylene alternating copolymer prepared by using a Ti complex having a substituted phenol type ligand. The copolymer has a styrene/ethylene alternating structure but has neither an ethylene chain nor styrene chains including head-to-head bonds and tail-to-tail bonds. The copolymer is a perfect alternating copolymer with an alternating degree of at least 70, preferably at least 90. However, as the ratio of ethylene to styrene is 50 % to 50 % by weight, it is difficult to vary the contents ofthe composition. The phenyl groups form isotactic streroregularity of which isotactic diad index is 0.92. As the copolymer has a molecular weight of 20,000 or below, the physical properties are poor. The catalyst has poor activity and a homopolymer such as syndiotactic polystyrene is obtained. Therefore, the polymerization method is not successfully commercialized.

Meanwhile, Macromol. Chem., 191, 2387 (1990) has reported a styrene/ethylene copolymer prepared by using CpTiCl₃ as a transition metal compound and methyl aluminoxane as a cocatalyst. The copolymer includes pseudo random copolymer with no styrene chains. The catalyst shows poor activity. The publication does not mention about stereoregularity ofthe phenyl groups.

Eur. Polym. J., 31, 79(1995) discloses a polymerization of ethylene and styrene using a catalyst of CpTiBz₃. According to the process, homopolymers such as polystyrene and syndiotactic polystyrene are obtained instead of copolymers of styrene/ethylene.

Macromolecules, 29, 1158 (1996) discloses polymerization of ethylene/styrene using CpTiC13 as a catalyst and a boron type cocatalyst, resulting to prepare a mixture of a copolymer having a high degree of alternating structure, a syndiotactic polystyrene and a polyethylene. The publication does not mention about stereoregularity of the phenyl groups .

U.S. Patent No. 5,883,213 discloses an ethylene/styrene copolymer having a weight average molecular weight of at least 81,000, having a styrene content of from 1 to less than 55 % by mole fraction, wherein the stereoregularity of phenyl groups in the alternating structure of ethylene and styrene is represented by an isotactic diad index of more than 0.75.

According to the catalyst disclosed in EP 0 416 815 A2, the yield of copolymer per metal unit is low, a larger amount of an organoaluminum compound is used, the polymerization process is carried out at a high temperature and a high pressure, and the polymer is amoφhous due to lack of stereoregularity. Further, the polymer has a pseudo-random structure.

Accordingly, the present inventors have developed new constrained geometry metaUocene catalysts for olefϊn/styrene copolymerization, which are superior to a conventional Ziegler-Natta catalyst in activity ofthe catalyst, content of styrene, amount of homopolymer prepared, and heterogeneous proportion ofthe polymer. Objects of the Invention

A feature ofthe present invention is the provision of a metaUocene catalyst of preparing ethylene/vinyl aromatic compound copolymer which is designed to improve low activity of catalyst, a low styrene content, an excess amount of homopolymer by-products and ununiform composition in the heterogeneous Ziegler-Natta catalyst system.

Another feature of the present invention is the provision of a metaUocene catalyst of preparing a large amount of ethylene/vinyl aromatic compound copolymer using a small amount of a cocatalyst.

A further feature ofthe present invention is the provision of a constrained geometry metaUocene catalyst with high activity.

A further feature ofthe present invention is the provision of a process of preparing an ethylene/vinyl aromatic compound copolymer using the metaUocene catalyst.

The above and other objects and advantages of this invention will be apparent from the ensuing disclosure and appended claims.

Summary of the Invention

The metaUocene catalyst according to the present invention contains in one molecule 2 to 4 transition metals that are bonded with ligands. The metaUocene catalyst is used for preparing an ethylene/vinyl aromatic compound copolymer. The metaUocene catalyst is employed with a cocatalyst such as organometallic compound or a mixture of non-coordinated Lewis acid and alkyl aluminum. The ethylene/vinyl aromatic compound copolymer prepared by using the metaUocene catalyst shows an isotacticity of at least 60 %, and especially an alternating index of at least 80 % measured by ¹³C NMR analysis.

Brief Description of the Drawings Fig. 1 is a chemical formula showing a microstructure of an ethylene/styrene copolymer;

Fig. 2 is a graph of the peak values of ethylene/styrene copolymers prepared in Example 7 and Comparative Example 1 measured by means of ¹³C NMR analysis; and

Fig. 3 is a chemical formula of an ethylene/styrene copolymer having an isotactic alternating structure.

Detailed Description of the Invention

The multi-nuclear constrained geometry catalyst according to the present invention is represented by the following formula (1), and the multi -nuclear constrained geometry catalysts containing 2, 3, or 4 transition metals are represented by the following formulae (2), (3) and (4), respectively:

where M is the same or different Ti, Zr or Hf;

Cp¹ is a non-substituted cyclopentadienyl group; a cyclopentadienyl group with 1 to 4 linear alkyl substitutes; an indenyl group; a substituted indenyl group; a tetrahydroindenyl group; a substituted tetrahydroindenyl group; a fluorenyl group; an octahydrofluorenyl group; a substituted fluorenyl group; an octahydrofluorenyl group; or a substituted octahydrofluorenyl group;

Y is a hydrogen atom or a silyl group of Cι__I0, an alkyl group of Cι_₁₀, an aryl group of Cj.io, or a combination thereof;

A is a hetero atom such as N, O, P, and S;

X is selected from the group consistmg of a hydrogen atom, a halogen atom, an alkyl group, an aryl group or a diene group; G is an alkyl group of cycloalkyl group of Cι.₃₀, an aryl group of Cι.₃₀, or an alkyl aryl group of Cι._30; and n is 2, 3, or 4.

In the present invention, the metaUocene catalyst is used with a cocatalyst. The cocatalyst is an organometallic compound such as alkyl aluminoxane and alkyl aluminum compound, which are known to an ordinary person in the art. The representative examples of alkyl aluminoxane are methyl aluminoxane (MAO) and modified methyl aluminoxane (MMAO). The alkyl aluminoxane includes an alkyl aluminoxane having a repeating unit ofthe following formula (5), a linear alkyl aluminoxane represented by the following formula (6), and a cyclic alkyl aluminoxane represented by the following formula (7):

where R is a hydrogen atom, an alkyl group of C^ or an aryl group of .₆, being same or different each other, and m and n are an integer of 0 — 100.

Alternatively, the co-catalyst of the present invention may be a mixture of different aluminoxanes, a mixture of aluminoxane and alkyl aluminum such as trimethyl aluminum, triethylaluminum, triisobutylaluminum and dimethyl aluminum chloride.

The molar ratio of aluminum of organometallic compound to transition metal of Group IV of metaUocene catalyst of the present invention is in the range from 1 : 1 to 1 10⁶ : 1, preferably from 10 : 1 to 1 x 10⁴ : 1.

The co-catalyst of the present invention can be a mixture of non-coordinated Lewis acid and alkyl aluminum. Examples of the non-coordinated Lewis acid include N, N-dimethyl anilinium tetrakis(pentafluorophenyl)borate, triphenylcarbenium tetrakis(pentafluorophenyl)borate, ferrocerium tetrakis (pentafluorophenyl)borate, and tris(pentafluorophenyl)borate, and the like.

Examples ofthe alkyl aluminum include trimethylaluminum, triethylaluminum, diethylaluminum chloride, dimethyl aluminum chloride, triisobutylaluminum, diisobutylaluminum and dimethylaluminum chloride, tri(n-butyl)aluminum, tri(n-propyl)aluminum, and triisopropylaluminum, and the like. The molar ratio of the non-coordinated Lewis acid to the transition metal in the catalyst system according to the present invention is preferably in the range from about 0.1 : 1 to about 20 : 1 and more preferably in the range of about 1 : 1. If the molar ratio of the alkyl aluminum to transition metal in the catalyst system is less than 0.01 : 1, it tends to be difficult to effectively activate the metal complex, and if it exceeds 100 : 1, such is economically disadvantageous.

To the copolymer of the present invention, additives or adjuvants which are commonly used for polymers, may be incorporated within a range not to adversely affect the effects of the present invention. Preferred additives or adjuvants mclude, for example, an antioxidant, a lubricant, a plasticizer, an ultraviolet ray absorber, a stabilizer, a pigment, a colorant, a filler and/or a blowing agent.

The polymerization temperature is usually from 0 to 200 °C, preferably from 30 to 150 °C. A polymerization temperature of -78 °C or lower is practically disadvantageous, and a temperature higher than 200 °C is not suitable, since decomposition of the metal complex will take place. The ethylene monomer polymerized by using the catalyst system of the present invention is an ethylene, an unsaturated ethylene having a substituted group, or an α, ω-diene. The ethylene monomer is copolymerized with a vinyl aromatic compound.

The representative examples of the vinyl aromatic compound include alkylstyrene, halogenated styrene, halogen-substituted alkyl styrene, alkoxy styrene, vinylbiphenyl, vinylphenylnaphthalene, vinylphenylanthracene, vinylphenylpyrene, trialkylsilylvinylbiphenyl, trialkylstanylvinylbiphenyl, alkylsilyl styrene, carboxymethyl styrene, alkyl ester styrene, vinyl benzene sulphonic acid ester, and vinylbenzyl dialkoxyphosphide. The representative examples of alkyl styrene are styrene, methyl styrene, ethyl styrene, butyl styrene, p-methyl styrene, p-tert-butyl styrene, and dimethyl styrene; those of halogenated styrene are chlorostyrene, bromostyrene, and fluorostyrene; those of halogen-substituted alkyl styrene are chloromethyl styrene, bromomethyl styrene, and fluoromethyl styrene; those of alkoxy styrene are methoxy styrene, ethoxy styrene, and butoxy styrene; those of vinyl biphenyl(?) are 4- vinyl biphenyl, 3-vinyl biphenyl, and 2-vinyl biphenyl; those of vinyl phenyl naphthalene are l-(4-vinylbiphenylnaphthalene), 2-(4-vinylbiphenylnaphthalene), 1 -(3-vinylbiphenylnaphthalene), 2-(3-vinylbiphenylnaphthalene), and l-(2-vinylbiphenylnaphthalene ); those of vinyl phenyl anthracene are l-(4-vinylphenyl)anthracene, 2-(4-vinylphenyl)anthracene, 9-(4-vinylphenyl)anthracene, 1 -(3-vinylphenyl)anthracene, 9-(3-vinylphenyl)anthracene, and l-(2-vinylphenyl)anthracene; those of vinyl phenyl pyrene are l-(4-vinylphenyl)pyrene, 2-(4-vinylphenyl)pyrene, l-(3-vinylphenyl)pyrene, 2-(3-vinylphenyl)pyrene, l-(2-vinylphenyl)pyrene, and 2-(2-vinylphenyl)pyrene; that of trialkyl silyl vinyl biphenyl is 4-vinyl-4-trimethyl silyl biphenyl; and those of alkyl silyl styrene are p-trimefhyl silyl styrene, m-trimethyl silyl styrene, o-trimethyl silyl styrene, p-triethyl silyl styrene, m-triethyl silyl styrene, and o-tri ethyl silyl styrene.

In the ethylenically unsaturated monomer, the representative examples of olefin are ethylene, propylene, 1-butene, 1-hexene and 1-octene; and those of cyclic olefin are cyclobutene, cyclopentene cyclohexene, 3 -methyl cyclopentene, 3 -methyl cyclohexene, and norbornene. Also, α, ω-diene means non-conjugated diene, and the examples are 1 ,4-pentadiene, 1 ,5-hexadiene, 1 ,6-heptadiene, 1 ,7-octadiene, 1 ,8-nonadiene, 1 ,9-decadiene, 1 ,4-hexadiene, dicyclopentadiene, 5-ethylene-2-norbornen, 5-vinyl norbornene, and methyl hexadiene. The content of the ethylenically unsaturated monomer in the copolymer is about 0 to 25 % by weight.

The weight average molecular weight (M_w) of ethylene/vinyl aromatic compound copolymer according to the present invention preferably exceeds 13,000, more preferably exceeds 20,000, and most preferably exceeds 30,000. The melt index (ATSM D-1238 procedure A, condition of E) is in the range from 0.001 to 1000, preferably in the range from 0.01 to 100, most preferably in the range from 0.1 to 30.

According to the present invention, monomers and solvent (if used) may be refined by vacuum distillation or by contacting alumna, silica, or Molecular Sieve before polymerization. Also, impurities may be eliminated by using a trialkyl aluminum compound, an alkali metal, or an alloy such as Na/K, etc.

It is preferable for the polymer of styrene/ethylene to have a styrene content of at least 0.1 mol%, more preferable 0.1 to 55 mol%. The polymer can be obtained at the pressure of 1 to 1 ,000 bar and at room temperature to 200 °C. The polymer obtained at higher temperature than the automatic polymerization temperature of each monomer contains a small amount of homopolymer prepared by free radical polymerization.

The copolymer of the present invention shows various physical properties depending upon the styrene content in the copolymer. The melting point decreases at the lower range of styrene content from about 0 to about 20 mol%, however, increases at the higher range of styrene content from about 20 to about 30 mol%. The melting point is constant when the styrene content reaches to a certain amount. In case that the styrene content is over 50 mol% and the alternative index is 0.85, the melting point (Tm) is 124 °C, which is much higher by about 30 °C comparing with the melting point of 90 °C disclosed in US Patent No. 5,883,213.

The polymer ofthe present invention is especially suitable for the thermoplastic elastomer used as a reinforcing material of thermoplastic or thermosetting copolymer. For the purpose of improving the physical properties, a synthetic and/or natural polymers may be blended thereto. Especially, an additional polymer such as polyethylene, ethylene/α-olefm copolymer, polypropylene, polyamide, aromatic polyester, polyisocyanate, polyurethane, polyacrylonitrile, silicon, and polyphenylene oxide may be blended with the copolymer ofthe present invention. The additional polymer is preferably employed in the amount of 0.5 to 50% by weight.

The ethylene/vinyl aromatic compound copolymer ofthe present invention is a material which retracts its original length after drawing to the length of 2 times at room temperature and exhibits physical properties of as an elastomer by ASTM Special Technical Bulletin No.184, a thermoplastic or thermosetting resin. Particularly, the copolymer of the present invention can be easily transformed not only by branching, grafting, hydrogenation, cross-linking but also by introducing functional groups to the double bonds, for example, by sulfonation or chlorination.

The present invention may be better understood by reference to the following examples, which are intended for the purpose of illustration and are not to be construed as in any way limiting the scope of the present invention, which is defined in the claims appended hereto.

Examples

Example 1: Preparation of Catalysts

(1) Preparation of [Me₄CpSi(Me)₂N-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NSi(Me)₂Me₄Cp]TiCl₂

2,3,4, 5-tetramethyl cyclopentadiene (2.45 g, 20 mmol) was dissolved in dried THF (30ml) in 100 ml nitrogen filled flask, and the solution was stirred while cooling to -78 ^°C using dry ice-acetone bath. To the solution was added n-butyl lithium (hexane solution of 1.6 M, 21 mmol) by a syringe, and then the temperature was raised to room temperature. After about 10 hours, the solvent was removed under vacuum, and then the residue was washed with pentane (50 ml x 3 times) and dried to obtain lithium tetramethylcyclopentanide (Cp*Xi⁺) with the yield of 98 %. To the resultant, 30 ml of THF solvent was injected and stirred, and Si(Me)₂Cl₂ (3.87 g, 30 mmol) was slowly added by a syringe at room temperature. After the reaction for over 5 hours, the solvent was removed under vacuum. The residue was refined and unreacted material was eliminated at about 70 ^°C to obtain greenish yellow chloro-2,3,4,5-tetramethylcyclopentadienylmethylsilane [Me₄CpSi(Me)₂Cl,] with the yield of 81 %.

(2) Preparation of Me₄CpSi(Me)₂NH-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NHSi(Me)₂CpMe₄

4,4-bi(4-aminophenyl propylidene)benzene of 6.89 g (20 mmol) was dissolved in THF (100 ml) and stirred in 250 ml nitrogen filled flask, and the solution was cooled to -78 ^°C using dry ice-acetone bath. To the solution was injected n-butyl lithium (hexane solution of 1.6 M, 42 mmol), and then the temperature was raised to room temperature. After about 10 hours, the solvent was removed under vacuum, and then the residue was washed with pentane and dried to obtain dilithium salt. The yield was 99 %. The dilithium salt was dissolved in THF (100 ml) and reacted with 12.9 g (60 mmol) of chloro-2,3,4,5-tetramethyl cyclopentadienyl methyl silane at -78 ^°C . After overnight reaction at room temperature, the temperature was raised to 70 ^°C .Then the solvent and unreacted material were removed under vacuum, and washed with pentane to obtain light yellow Me₄CpSi(Me)₂NH-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NHSi(Me)₂CpMe₄ with the yield of 76 %. (3) Preparation of [Me₄CpSι(Me)₂N-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NSi(Me)₂CpMe₄] ⁴-4Li⁺4THF

Me₄CpSi(Me)₂NH-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NHSi(Me)₂Me₄Cp of 7.01 g (10 mol) was dissolved in THF (50 ml) and stirred in 100 ml nitrogen filled flask, and the solution was cooled to -78 ^°C using dry ice-acetone bath. To the solution was injected n-butyl lithium (hexane solution of 1.6 M, 42 mmol), and then the temperature was raised to room temperature. After about 10 hours, the solvent was removed under vacuum, and then the residue was washed with pentane and dried to obtain light yellow THF coordinated tetralithium salt with the yield of 95 %.

(4) Preparation of [Me₄CpSi(Me)₂N-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NSi(Me)₂CpMe₄] ^4"4MgCf4THF

Me₄CpSi(Me)₂NH-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NHSi(Me)₂CpMe₄ of 7.01 g (10 mmol) was dissolved in the mixture of THF and toluene (50ml, v/v=l : 4) and stirred in 100 ml nitrogen filled flask. To the solution was injected isopropyl magnesium chloride (42 mmol) and reacted with refluxing for over 10 hours. The solvent was removed under vacuum, and then the residue was washed with pentane and dried to obtain light pink THF coordinated tetramagnesium salt with the yield of 97 %.

(5) Preparation of [Me₄CpSi(Me)₂N-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NSi(Me)₂CpMe₄]Ti₂Cl₄

[Me₄CpSi(Me)₂N-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NSι(Me)₂CpMe₄]^4'4Li⁺4 THF of 2.10 g (2.07 mmol) was dissolved in THF (30 ml) and stirred in 100 ml nitrogen filled flask. To the solution was slowly injected TiCl₃ ^• 3THF (1.54 g, 4.14 mmol) /THF (20 πrδ). After 2 hours, a large excess amount of CH₂C1₂ was added by a syringe and reacted for 3 hours. After completion of the reaction, the solvent was removed. The residual solid was extracted with toluene, and the liquid was concentrated.

[Me₄CpSι(Me)₂N-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NSι(Me)₂CpMe₄]Tι₂Cl₄ was obtained as a yellowish orange crystalline material after being recrystallized from the solvent mixture of hexane and toluene at -30 ^°C with the yield of 31 %.

Example 2: Preparation of Catalyst

Example 2 was carried out in the same manner as m Example 1 except that

AgCl was used instead of CH₂C1₂

[Me₄CpSι(Me)₂N-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NSι(Me)₂CpMe₄]Tι₂Cl₄ was obtained as a yellowish orange crystalline material and the identification was confirmed by NMR. The yield was 34%.

Example 3: Preparation of Catalyst

Example 3 was carried out m the same manner as m Example 1 except that tetramagnesium salt was used instead of tetralithium salt and the reaction time is over 10 hours.

[Me₄CpSι(Me)₂N-C₆H₄-C(Me)₂-C₅H₄-C(Me)₂-C₆H₄-NSι(Me)₂CpMe₄]Tι₂Cl₄ was obtained and identified by NMR The yield was 41%.

Example 4: Preparation of Catalyst

Example 4 was carried out in the same manner as in Example 1 except that AgCl was used instead of CH₂C1₂

[Me₄CpSι(Me)₂N-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NSι(Me)₂CpMe₄]Tι₂Cl₄ was obtained and identified by NMR The yield was 45% Examples 5-8: Preparation of Polymers

Polymerization was carried out in an electro-heating glass autoclave having a capacity of 1 liter or a metal autoclave having a capacity of 2 liters, which was equipped with a magnetic stirrer and completely substituted by nitrogen by repeating evacuation and nitrogen substitution. Cooling water flew through the cooling coil equipped in the reactor. A solvent such as hexane or toluene, to which Na was added and distilled, was used. The solution was contacted with Molecular Sieve, alumina, or silica under nitrogen gas.

Example 5: Homopolymerization of Ethylene

In a metal autoclave having a capacity of 2 liters, hexane (100 ml) and MAO (10 mmol, Al) were charged, and the temperature of the solution was raised to 70 ^°C while stirring.

[Me₄CpSi(Me)₂N-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NSi(Me)₂Me₄Cp]TiCl₂ containing 20 μmol of Ti was polymerized with ethylene at 10 bar. After 30 minutes, ethylene gas was released. After adding a mixed solution of hydrochloric acid/methanol to stop the reaction and wash it, polyethylene was obtained in a state of powder. The product was dried under reduced pressure to obtain 59 g of polyethylene.

Example 6: Copolymerization of Ethylene/1-Octene

In a metal autoclave having a capacity of 2 liters, hexane (1,000 ml),

1-octene (50 ml), and MAO (10 mmol, Al) were charged, and the temperature of the solution was raised to 70 ^°C while stirring.

[Me₄CpSi(Me)₂N-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NSi(Me)₂Me₄Cp]TiCl₂ containing 20 μmol of Ti was polymerized with ethylene at 10 bar. After 30 minutes, ethylene gas was released. After adding a mixed solution of hydrochloric acid/methanol to stop the reaction and wash, copolymer was obtained. The product was dried under reduced pressure to obtain 65 g ofthe ethylene/ 1-octene copolymer. ¹³C NMR analysis of the copolymer showed that the content of 1-octene is 8.4 mol%, and T_m was 98 ^°C .

Example 7: Copolymerization of Ethylene/Styrene

In a glass autoclave having a capacity of 1 liter, SM (200 ml) and MAO (10 mmol, Al) were charged, and the temperature of the solution was raised to 70 ^°C while stirring.

[Me₄CpSi(Me)₂N-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NSi(Me)₂Me₄Cp]TiCl₂ containing 20 μmol of Ti was polymerized with ethylene at 4 bar. In the process of polymerization, a polymer insoluble in a solvent was produced in a state of powder. After 30 minutes, ethylene gas was released. After adding a mixed solution of hydrochloric acid/methanol to stop the reaction and wash, ethylene/styrene copolymer was obtained in a state of powder. The product was dried at 130^°C for 6 hours under reduced pressure to obtain 15 g of the copolymer. ¹³C NMR analysis showed that it was an isotactic alternating copolymer containing 50.2 mol% of styrene. The isotacticity (diad) was 0.62 and the alternating index was 0.82.

Example 8: Copolymerization of Ethylene/Styrene

In a metal autoclave having a capacity of 2 liters, SM (1 ,000 ml) and MAO (10 mmol, Al) were charged, and the temperature of the solution was raised to 70 ^°C while stirring.

[Me₄CpSi(Me)₂N-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NSi(Me)₂Me₄Cp]TiCl₂ containing 20 μmol of Ti was polymerized with ethylene at 10 bar. After 30 minutes, ethylene gas was released. After adding a mixed solution of hydrochloric acid/methanol to stop the reaction and wash, ethylene/styrene copolymer was obtained in a state of powder. The product was dried at 130 ^°C for 6 hours under reduced pressure to obtain 49 g ofthe copolymer. ¹³C NMR analysis showed that it was an isotactic alternating copolymer containing 50.8 mol% of styrene. The isotacticity (diad) was 65 % and the alternating index was 84 %.

Comparative Example 1 : Copolymerization of Ethylene/Styrene

Comparative Example was conducted in the same manner as Example 1 except that [Cρ(Me)₄-Si(Me)₂-N-t-Bu]TiCl₂(CGC) was used instead of the catalyst of Example 1. Copolymer of 8.5 g was obtained after being dried at 130 ^°C for 6 hours under reduced pressure. ¹³C NMR analysis showed that it was a pseudo-random copolymer containing 35.3 mol% of styrene. The alternating index was 41 %.

Comparative Example 2: Copolymerization of Ethylene/Styrene

Comparative Example was conducted in the same manner as Example 1 except that rac- [C₂H₄(Ind)₂]ZrCl₂ was used instead ofthe catalyst of Example 1. Copolymer of 62 g was obtained after being dried at 130 ^°C for 6 hours under reduced pressure. ¹³C NMR analysis showed that it was a pseudo-random copolymer containing 7.9 mol% of styrene. The isotacticity (diad) was 71 % and the alternating index was 21 %.

The polymer specimens of 40-50 mg of Examples 7- 8 and Comparative Examples 1-2 were dissolved in about 5 ml of a hot solvent mixture of trichlorobenzene and benzene, and the resulting solution was put into a 5 mm NMR tube, and then analyzed by means of 100 MHz ^I3C NMR. The test results are shown in Table 1. Table 1

Examples Comparative Examples

7 8 1 2

Catalyst catalyst^a) catalyst³ ' CGC^b) EBIZ^C)

SM (ml) 200 1000 200 200

C2 (kg/cm²) 4 10 4 4

Mw ( x l0⁴) 3.88 11.3 4.12 0.61

MWD 2.09 3.26 2.23 3.54

TM (^°C) 124.1 124.5 - 91.2

Styrene content (mol%) 50.2 50.1 35.3 7.9

Isotacticity (diad, %) 63 65 - 71

Alternating index (%) 82 83 41 21

* Polymerization conditions : catalyst (20 μmol), MAO/Ti=500, 70 ^°C , 30 minutes Notes: a) is

[Me₄CpSi(Me)₂N-C₆H₄-C(Me)₂-C₆H₄-C(Me)₂-C₆H₄-NSi(Me)₂CpMe₄]TiCl₂ ofthe catalyst in Examples 7 and 8; b) is CGC, namely [Cρ(Me)₄-Si(Me)₂-N-t-Bu]TiCl₂; and c) is EBIZ, namely rac- [C₂H₄(Ind)₂]ZrCl₂

As shown in Table 1 , the ethylene/styrene copolymers by using the catalyst ofthe present invention have a higher styrene content as compared with conventional copolymers by using CGC or EBIZ (rac-ethylenebisindenylzirconium chloride, a common catalyst for iPP copolymerization), especially, as compared with Comparative Example 2 by using a zirconium catalyst. Further, the alternating index is very high compared with those of Comparative Examples 1 and 2. Also, the higher isotacticities of Examples 7 and 8 over 60 % show that the copolymer of the present mvention is a semi-crystalline copolymer having the melting point of 125 ^°C even at a high styrene content. Such result is superior to the result disclosed in US Patent No. 5,883,213, in which a copolymer containing styrene of 49 mol% and having a higher isotacticity over 95 % and an alternating index of 55 % has a melting point of about 90 ^°C . It may be caused by the high alternating index. The product is a new isotactic alternating ethylene/styrene copolymer.

The microstructure of ethylene/styrene copolymer identified by ¹³C NMR is shown in Fig. 1., and the analysis of ¹³C NMR chemical shift is shown in Table 2.

Table 2

Carbon Chemical shift (ppm)

S_β 3 25.80

S_p y + 27.89

\ Ϊ > N y ⁺ 29.99

S_α y + 35.06 α y 37.05

41.61

T 45.2-46.6

In Fig. 1 and Table 2, S is a secondary carbon and T is a methine bonded to a phenyl group of styrene as a tertiary carbon, α , β and y mean that a phenyl- substituted secondary carbon is located at 2, 3, and 4 position of itself respectively. For example, S_{α γ} is a secondary carbon having a phenyl substituted secondary carbon at its 2 position on one side and a secondary carbon at its 4 position on the other side. Further, "+" means that a secondary carbon exists over 5 position of itself. The structures ofthe copolymers prepared in Examples 7 ~ 8, and

Comparative Examples 1 ~ 2 were analyzed by means of ¹³C NMR, and the comparison result of Example 7 and Comparative Example 1 is shown m Fig. 2. ¹³C NMR analyst was carried out by using a mixed solvent of trichlorobenzene and benzene at 100^°C and TMS(tπmethyl silane). Such copolymer was substantially soluble in THF or CHC1₃ by more than 91% by weight at room temperature, and completely soluble in boiling THF.

Distinctively, in the ethylene/styrene copolymer prepared in Example 7, the integral near 25 ppm attributable to the alternating structure was high compared with that of pseudo-random copolymer. Further, the peak attributable to the ethylene cham was nearly not observed m the vicinity of 30 ppm. It indicates that the polymer has an alternating structure. Also, S_{α α} peak attributable to a head-to-tail structure of styrene was nearly not observed m the vicinity of 42 ppm. It indicates that there is no styrene chain having a styrene-styrene structure.

The diad (mm) integral at 45.2 ppm is measured by the peak attributable to a secondary carbon observed m the range of 45.2 to 46.6 ppm, and the isotacticity was measured by the ratio to integral of the total secondary carbon In Examples 7 and 8, the isotacticities were 63 % and 65 % respectively, as shown in Table 1 , which are different from those ofthe conventional pseudo-random copolymers

Accordingly, the multi-nuclear constrained geometry catalyst ofthe present invention improves the styrene content and is especially useful to prepare isotactic alternating ethylene/styrene copolymer, compared with the conventional constrained geometry catalysts. The copolymer has high activity of polymerization and exceedingly improves styrene content, as compared with a traditional ethylene/styrene copolymer, at the same polymerization condition New copolymer having a higher alternating index over 80 % and a stereoregularity of about 60 % can be obtained. Further, a new semi-crystalline copolymer with a high styrene content, which has the melting point of about 125 ^°C , can be prepared.

In the above, the present invention was described based on the preferred embodiment of the present invention, but it should be apparent to those ordinarily skilled in the art that various changes and modifications can be added without departing from the spirit and scope ofthe present invention. Such changes modifications should come within the scope ofthe present invention.

Claims

What is claimed is:

1. A process for preparing ethylene/vinyl aromatic compound copolymer which comprises copolymerizing an unsaturated ethylene monomer or an α,ω-diene monomer with a vinyl aromatic compound monomer under a catalyst system consisting of a multi-nuclear constrained geometry metaUocene catalyst represented by the following formulae (1)~(4) as a catalyst and an organometallic compound or a mixture of non-coordinated Lewis acid and alkyl aluminum as a cocatalyst:

where M is the same or different Ti, Zr or Hf;

Y is a hydrogen atom or a silyl group of C ₀, an alkyl group of Cι._]0, an aryl group of Cj.io, or a combination thereof;

A is a hetero atom selected from the group consisting of N, O, P and S; X is selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, an aryl group or a diene group;

G is an alkyl group of C].₃₀, a cycloalkyl group of C].₃₀, an aryl group of Cι.₃₀, or an alkyl aryl group of C^o_; and n is 2, 3, or 4.

2. The process as in Claim 1 wherein said organometallic compound is an alkyl aluminoxane or an organoaluminum compound.

3. The process as in Claim 2 wherein said alkyl aluminoxane is methyl aluminoxane (MAO) or a modified methyl aluminoxane (MMAO).

4. The process as in Claim 2 wherein said organoaluminum compound contains the unit represented by following formula (5), and is a linear or cyclic aluminoxane represented by the following formula (6) or (7):

where R is a C_\.₆ alkyl group_> and m and n are an integer of from 0 to 100.

5. The process as in Claim 1 wherein said non-coordinated Lewis acid is selected from the group consisting of N,N' -dimethyl aniline tetrakis(pentafluorophenyl) borate, triphenyl carbenium tetrakis(pentafluorophenyl) borate, ferrocerium tetrakis(pentafluorophenyl) borate, and tris(pentafluorophenyl) borate; said alkyl aluminum being selected from the group consisting of trimethyl aluminum, triethyl aluminum, diethyl aluminum chloride, dimethyl aluminum chloride, triisobutyl aluminum, diisobutyl aluminum chloride, tri(n-butyl)aluminum, tri(n-propyl)aluminum, and triisopropyl aluminum.

6. The process as in Claim 1 wherein the molar ratio of aluminum in the organometallic compound to the transition metal in the metaUocene catalyst is in the range of about 1 : 1 to about 10⁶ : 1.

7. The process as in Claim 1 wherein the molar ratio of said non-coordmated Lewis acid to the transition metal m the metaUocene catalyst is in the range of about 0.1 : 1 to about 20 : 1.

8. The process as m Claim 1 wherem said ethyl ene/aromatic vmyl compound copolymer is copolymeπzed at the temperature of 0 ~ 200 ^°C .

9. The process as m Claim 1 wherem said ethylene/vinyl aromatic compound copolymer includes an antioxidant, a lubricant, a plasticizer, an ultraviolet absorber, a stabilizer, a pigment, a staining agent, a filler, and/or a blowing agent.

10. An ethyl ene/vmyl aromatic compound copolymer prepared in accordance with the process of Claim 1.

1 1. An ethyl ene/vmyl aromatic compound copolymer as in Claim 10 wherem said copolymer has an ethylene content of about 45-99 mol% and a vmyl aromatic compound content of about 1-55 mol%.

12. An ethyl ene/vmyl aromatic compound copolymer as m Claim 10 wherem said copolymer has a weight average molecular weight of greater than about 13,000 and a melt index of about 0.001 - 1 ,000.

13. An ethylene/vinyl aromatic compound copolymer as in Claim 10 wherem said copolymer has an isotacticity diad of greater than 60 % and an alternating index of greater than 80 %.

14. An ethylene/vinyl aromatic compound copolymer as m Claim 10 wherem said copolymer does not have a peak attributable to the head-to-tail structure of styrene m the vicinity of 42 ppm when analyzed by means of ¹³C NMR using TMS.

15. A blend of the ethylene/vinyl aromatic compound copolymer of Claim 10 to which a polymer selected from the group consisting of polyethylene, ethylene/α-olefϊn copolymer, polypropylene, polyamide, aromatic polyester, polyisocyanate, polyurethan, polyacrylonitryl, silicon, and polyphenyloxide is added in the amount of about 0.5 to 50 % by weight.