JPH04337308A - Production of block copolymer - Google Patents

Abstract

PURPOSE:To obtain the title copolymer having excellent balance of impact resistance and stiffness by polymerizing ethylene with propylene in the presence of a specific transition metal compound and organic aluminum under specific conditions. CONSTITUTION:At first, propylene or propylene or propylene and <=6wt.% ethylene is polymerized in the presence of a transition metal compound expressed by the formula (A is 6-20C substituted cyclopentadienyl; N is Si; R is 1-20C hydrocarbon residue; X is 1-10C hydrocarbon residue or halogen; M is titanium, zirconium or hafnium) and an organoaluminum (preferably used at an amount of 50-5000mol based on the compound expressed by the formula) such as trimethylaluminum so as to become rate of polymerization of 40-95% based on total polymer and then ethylene and propylene having a weight ratio of (10/90)-(95/5) are polymerized so as to become rate of polymerization of 60-5% based on total polymer to provide the objective copolymer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing block copolymers. Specifically, the present invention relates to a method for producing a block copolymer, which comprises block copolymerizing propylene and ethylene using a specific catalyst.

0002

[Prior art] In order to improve the impact resistance of polypropylene, especially at low temperatures, a block copolymer of impact resistant propylene is produced by first polymerizing propylene alone and then copolymerizing ethylene and propylene. This is well known, and many improvements have been made and reported since the physical properties of the resulting polymer vary depending on the catalyst and polymerization method used.

0003

[Problem to be solved by the invention] Although products with considerably excellent physical properties can be obtained by the above-mentioned block copolymerization method, the requirements for physical properties of copolymers are becoming increasingly strict, and the development of copolymers with even more excellent physical properties. is desired.

0004

[Means for Solving the Problems] The present inventors have completed the present invention by intensively searching for a method for solving the above-mentioned problems and producing a copolymer with an excellent balance between impact resistance and rigidity.

That is, the present invention provides the following general formula (2) (wherein A
is a substituted cyclopentadienyl group having 6 to 20 carbon atoms, N is a silicon element, R is a hydrocarbon residue having 1 to 20 carbon atoms, X is a hydrocarbon residue having 1 to 10 carbon atoms or a halogen atom, M
is a metal atom selected from titanium, zirconium, and hafnium. ) in the presence of a transition metal compound represented by 10
This is a method for producing a block copolymer, which is characterized in that the polymerization is carried out at a weight ratio of /90 to 95/5, which accounts for 60 to 5% by weight of the total polymer.

[0006]

embedded image The transition metal compound used in the present invention is represented by the above general formula 2, where A is a substituted cyclopentadienyl group having 6 to 20 carbon atoms, preferably a cyclopentadienyl group. Examples include those in which 1 to 4 hydrogen atoms are substituted with an alkyl group having 1 to 5 carbon atoms, particularly preferably those in which 2 to 4 hydrogen atoms in a cyclopentadienyl group are substituted with a methyl group. N is a silicon element, and R has 1 to 20 carbon atoms.
Examples include hydrocarbon residues, preferably hydrocarbon residues having 1 to 10 carbon atoms, particularly preferably alkyl groups and allyl groups having 1 to 6 carbon atoms. X is a hydrocarbon residue having 1 to 10 carbon atoms or a halogen atom, preferably an alkyl group having 1 to 3 carbon atoms or chlorine. M is titanium,
A metal atom selected from zirconium and hafnium, with particular examples of zirconium and hafnium.

[0007] As the organoaluminum compound used in the present invention, aluminoxane which is a condensate of aluminum is preferably used, and linear or cyclic aluminoxane having a degree of polymerization of about 5 to 100, especially one having a methyl group as an alkyl group. is preferably used. Here, the ratio of aluminoxane used to the above transition metal catalyst component is 10 to 1,000,000 times by mole, usually 50 to 5,000 times by mole.

[0008] Also, organic aluminum containing 1 to 1 carbon atoms
Alkylaluminum compounds in which 1 to 3 alkyl residues of 2 are bonded are preferably used, and specifically, trimethylaluminum, triethylaluminum, triisopropylaluminium, tributylaluminium, dimethylaluminum chloride, diethylaluminum chloride, diisopropylaluminum chloride. , diisopropylaluminium isopropoxide, ethylaluminum dichloride, ethylaluminum diisopropoxide, and the like.

Among these aluminum compounds, trialkyl aluminum compounds are particularly preferably used, and in this case, a combination of an alkyl aluminum and a stable anion, or a compound that generates it, is used.

Examples of stable anions or compounds that generate them include ionic compounds formed from ion pairs of cations and anions and electrophilic compounds. These compounds are usually known as Lewis acid compounds, and have appropriate Lewis acidity, and have the property of converting into ionic compounds by reacting with neutral metallocene compounds used as catalysts. A compound that is necessary and reacts with the transition metal compound represented by the above general formula 2, and the group represented by X in the above general formula 2 transfers as an electron pair to the Lewis acid compound to generate a transition metal cation compound. The Lewis acid itself or the anion that forms an ion pair does not recombine or strongly coordinate with the generated transition metal cation compound to inactivate the polymerization activity.

The ratio of the organoaluminum compound to the transition metal compound in the solution is preferably 1 to 100,000 times, usually 1 to 5,000 times, the aluminum atom to the transition metal atom. Of course, there is no problem even if an excess of the organoaluminum compound is used, but the polymerization effect remains the same, and it is necessary to strengthen the post-treatment.

Examples of the hydrocarbon solvent used in the polymerization in the present invention include aliphatic hydrocarbon compounds such as propane, butane, pentane, hexane, heptane, octane, nonane, decane, hexadecane, cyclopentane, and cyclohexane. Aromatic hydrocarbon compounds such as benzene, toluene, xylene, and ethylbenzene, and ether or ester compounds such as diethyl ether and tetrahydrofuran can also be used. Halogenated hydrocarbon compounds such as methylene chloride can also be used if they do not react with the organoaluminum compound used.

What is important in the present invention is that propylene alone or a copolymer of up to 6% by weight of ethylene is first polymerized to 40 to 95% by weight of the total polymer, and then ethylene and propylene are mixed in a ratio of 10/90 to 95/1. 5% by weight of the total polymer. If the initial polymerization is less than 40% by weight of the total polymer, the rigidity will be poor, and if the ethylene content exceeds 6% by weight, the rigidity will be poor, which is not preferred. As for the molecular weight, it is preferable that the intrinsic viscosity measured in a tetralin solution at 135 DEG C. is about 0.5 to 10, particularly about 0.7 to 5. In addition, the isotactic pentad fraction measured by 13C-NMR of the polymer obtained in the first stage polymerization is 0.8 or more, preferably 0.9 or more, and especially 0.95 or more to obtain a good balance of physical properties. This is preferable in that it keeps the

Further, in the subsequent polymerization, if ethylene and propylene are polymerized in a ratio smaller than 10/90 weight ratio, the impact resistance will be poor, and if the weight ratio is larger than 95/5, the impact resistance will be poor. As for the molecular weight, it is preferable that the intrinsic viscosity measured in a tetralin solution at 135 DEG C. is about 0.5 to 20, particularly about 1.0 to 10.

There are no particular limitations on the polymerization conditions, and solvent polymerization using an inert medium, bulk polymerization in which an inert medium is not substantially present, and gas phase polymerization can also be used. Generally, the polymerization temperature is -100 to 200 DEG C., and the polymerization pressure is normal pressure to 100 kg/cm2. Preferably -100 to 100°C, normal pressure to 5
0 kg/cm2.

[0016] Also, during polymerization, α-olefins having 4 or more carbon atoms, such as butene-1, pentene-1, hexene-1, heptene-1, and 4-methylpentene-1, are converted to propylene in an amount of 10% by weight or less. Physical properties such as transparency can also be improved by using it. If it exceeds 10% by weight, the physical properties will be poor, which is not preferable.

[0017]

[Examples] The present invention will be further explained by showing examples below.

Example 1 Dimethylsilylbis(2,4
1 mg of dimethylsilylbis(2,4-dimethylcyclopentadienyl) zirconium dichloride obtained by lithiation of (dimethylcyclopentadienyl) and reacting with zirconium tetrachloride is dissolved in 10 ml of toluene,
Methylaluminoxane (manufactured by Tosoh Akzo) 670mg
to make a catalyst component solution, and 1.5 kg of propylene
It was inserted into an autoclave with a volume of 5 liters. Then, polymerization was carried out for 2 hours while maintaining the internal temperature at 15°C. Then, ethylene was added to 5 kg/cm2-G, the internal temperature was raised to 30 DEG C., and polymerization was carried out for 10 minutes while maintaining the ethylene partial pressure.

After completion of polymerization, unreacted monomers are purged,
The contents were taken out and dried to obtain 456 g of polymer. The intrinsic viscosity (hereinafter referred to as η) measured with a tetralin solution at 135° C. was 1.48, and the ethylene content was 5.6% by weight. The melt flow index (ASTM D1238) at 230° C. of the product granulated by adding 2,6-di-t-butyl-4-methylphenol was 8.7. In addition, a sheet with a thickness of 1 mm was prepared, and the tensile yield point stress (ASTM D-638) and bending stiffness (AS
TM D747), Izod impact strength (ASTM
D256 (-10°C, 23°C) was measured to be 238 kg/cm2, 7200 kg/cm2, respectively.
They were 48 kg·cm/cm 2 and 38 kg·cm/cm 2 . When the propylene homopolymerization was completed, the polymerization was stopped and the polymer was taken out and measured by 13C-NMR, and the isotactic pentad fraction was found to be 0.97. Further, the copolymerized portion calculated by model polymerization was 42% by weight.

Comparative Example 1 Using 100 mg of a commercially available highly active titanium trichloride catalyst (TG21, manufactured by Marubeni Solvay Co., Ltd.) and 1 ml of diethylaluminium chloride, the polymerization temperature was changed to 65°C for propylene alone, and 65°C for polymerization with ethylene. Copolymerization at 50℃
In addition, when polymerizing propylene alone, hydrogen is added to 5
．． 5NL was used. Copolymerization time: 30 minutes, 45 minutes, 6
Ethylene content as 0 minutes, 11.5%, 14.8%
, 18.6%, three types of copolymers with ethylene contents were synthesized and similarly evaluated. Melt flow index, tensile yield point stress, bending stiffness, Izod impact strength (-10℃
, 23°C) with 11.5% ethylene content: 9.5g/10min, 285kg/cm2,
9800kg/cm2, 7.2 kg・cm/cm,
3.2kg・cm/cm, ethylene content 14.8%
The one is 8.1g/10min, 235kg/cm2
, 6800kg/cm2, 14.5 kg・cm/
cm, 4.5kg・cm/cm, ethylene content 1
8.6% is 6.9g/10min, 165kg
/cm2, 5100kg/cm2, 22.5 kg
・cm/cm, 16.3kg・cm/cm,
The isotactic pentad fraction of polypropylene obtained from the propylene homopolymerization part is 0.97, and MW/MN
was 6.5.

Example 2 Copolymerization with ethylene was carried out at an ethylene partial pressure of 8 kg/cm2-G.
After polymerization for 5 minutes, a product with an ethylene content of 8.2% by weight was obtained. Physical properties were similarly measured, including melt flow index, tensile yield point stress, bending stiffness, and Izod impact strength (
-10℃, 23℃) are 6.2g/10mi, respectively.
n, 285kg/cm2, 9800kg/cm2, 2
4.9kg・cm/cm, 8.5kg・cm/
It was cm. In addition, when the propylene homopolymerization is completed, the polymerization is stopped and the polymer is taken out and 13C-NM
The isotactic pentad fraction measured by R was 0.97. Further, the copolymerized portion calculated by model polymerization was 25% by weight.

[0022]

[Effects of the Invention] By carrying out the method of the present invention, a copolymer having an excellent balance of physical properties can be obtained, which is extremely valuable industrially.

[Brief explanation of drawings]

FIG. 1 is a flow diagram to aid understanding of the present invention.

Claims (2)

[Claims] [Claim 1] Chemical formula 1 of the following general formula (wherein A is 6 carbon atoms)
~20 substituted cyclopentadienyl groups, N is silicon element,
R is a hydrocarbon residue having 1 to 20 carbon atoms, and X is a hydrocarbon residue having 1 to 1 carbon atoms.
0 hydrocarbon residue or halogen atom, M is titanium,
A metal atom selected from zirconium and hafnium. ) in the presence of a transition metal compound represented by 10/90-9
A method for producing a block copolymer, which comprises polymerizing the block copolymer at a weight ratio of 5/5 to 60 to 5% by weight of the total polymer. [Chemical formula 1] 2. The method according to claim 1, wherein the substituted cyclopentadienyl group is one in which 1 to 5 hydrogen atoms of the cyclopentadienyl group are replaced with hydrocarbon residues.