JP2764074B2 - Method for producing syndiotactic polypropylene - Google Patents

Description

The present invention relates to a method for producing syndiotactic polypropylene. More specifically, it relates to a method for producing syndiotactic polypropylene in a high yield per catalyst.

(Prior art)

Syndiotactic polypropylene has long been known for its existence, but conventional methods of low-temperature polymerization with a catalyst consisting of a vanadium compound, ether and organoaluminum have poor syndiotacticity, which is characteristic of syndiotactic polypropylene. It was hard to say. On the other hand, JAEWEN et al., For the first time, were able to obtain polypropylene with good tacticity such that the syndiotactic pentad fraction exceeds 0.8 using a catalyst composed of a transition metal catalyst component having an asymmetric ligand and an aluminoxane. Was discovered (J.Am.C
hem. Soc., 1988, 110, 6255-6256).

[Problems to be solved by the invention]

The above-mentioned method by JAEWEN et al. Is an excellent method having good activity per transition metal and high tacticity of the obtained polymer, but the catalyst is unstable and the reproducibility of the activity of the catalyst is poor. There was a problem in manufacturing on an industrial scale.

[Means for solving the problem]

The present inventors have diligently studied a method for solving the above problems and producing polypropylene having high activity and high syndiotacticity, and completed the present invention.

That is, the present invention provides propylene using a catalyst comprising a transition metal catalyst component selected from isopropyl (cyclopentadienyl-1-fluorenyl) hafnium dichloride and isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride and aluminoxane. In the polymerization method, after a transition metal catalyst component and an aluminoxane are contacted in the presence of propylene in a small amount of aromatic hydrocarbon compound to polymerize propylene, propylene is polymerized in the presence of liquid propylene using the slurry. A method for producing syndiotactic polypropylene.

In the present invention, the transition metal catalyst component is isopropyl (cyclopentadienyl-1-fluorenyl) hafnium dichloride or isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride described in the above document.
General formula, (Wherein R is a hydrocarbon residue having 1 to 3 carbon atoms). Examples thereof include methylaluminoxane wherein R is a methyl group and n is 5 or more, preferably 10 or more. . The use ratio of aluminoxane to the transition metal catalyst component is 10 to 100,000,000 mole times, usually 50 to 5000.
It is molar times.

What is important in the present invention is that, prior to performing bulk polymerization in the presence of liquid propylene, the transition metal catalyst component and aluminoxane are contacted in the presence of propylene in the aromatic hydrocarbon compound to polymerize propylene. Here, the ratio of the aluminoxane to the transition metal catalyst component may be the same as the condition for performing the bulk polymerization, or may be performed using a part thereof. The polymerization in the aromatic hydrocarbon is preferably performed until 0.1 g or more and 10,000 g or less of propylene is polymerized per 1 g of the transition metal catalyst component.At 0.1 g or less, the effect of improving the activity is small. The device is bulky and not preferred, nor is it more effective.

Aromatic hydrocarbon compound is 10 per g of transition metal catalyst component.
It is preferable to use 1 to 1000000 ml. If the amount is 10 ml or less, the effect of improving the activity is small, and if it is 10000 ml or more, the activity in bulk polymerization is not sufficient. The volume is more preferably 1,000 to 100,000 ml. It is preferable to use 10 ml or more of liquid propylene per 1 ml of the aromatic hydrocarbon compound from the viewpoint of activity in bulk polymerization.

As the polymerization temperature, polymerization in an aromatic hydrocarbon solvent, or in bulk polymerization is generally carried out at -100 to 200 ° C, and polymerization in an aromatic hydrocarbon solvent is usually lower than that in bulk polymerization. It is common to do with. As the polymerization pressure, polymerization in an aromatic hydrocarbon solvent is from normal pressure to 10 kg / cm ²
Generally, the bulk polymerization is performed under pressure conditions under which propylene becomes liquid. .

In the present invention, propylene polymerization means not only propylene homopolymerization but also ethylene and butene-1 up to about 20% by weight.
And the production of copolymers with other α-olefins.

There is no particular limitation on the method of transition from polymerization in an aromatic hydrocarbon solvent to bulk polymerization, but usually an aromatic hydrocarbon solvent slurry is introduced into liquid propylene, or a liquid is added to the aromatic hydrocarbon solvent slurry. By adding propylene.

In the present invention, as the aromatic hydrocarbon compound, an aromatic hydrocarbon compound having 6 to 20 carbon atoms in a liquid state under the reaction conditions is used, and specifically, benzene, toluene, xylene,
Examples thereof include those in which a part or all of hydrogen of benzene such as ethylbenzene and tetralin is substituted by an alkyl residue having 1 to 12 carbon atoms, or a reactive alkyl-substituted naphthalene.

〔Example〕

 Hereinafter, the present invention will be described with reference to Examples.

Example 1 An autoclave having an internal volume of 200 ml was charged with 100 ml of toluene, isopropylcyclopentadienyl-1-fluorene synthesized according to a conventional method was lithium-treated, and isopropyl (cyclopentadienyl-fluorene) obtained by reacting with zirconium tetrachloride was used. 5 mg of 1-fluorenyl) zirconium dichloride was added thereto, and propylene was charged to 2 kg / cm ² -G. Then, a solution prepared by dissolving 0.67 g of methylaluminoxane of Toyo Akzo Co., Ltd. having a degree of polymerization of about 15 in 10 ml of toluene was added.
Polymerized for minutes. When a part was sampled and analyzed, 600 g of propylene was polymerized per 1 g of isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride. Then unreacted propylene was removed and the slurry was 5 l.
Was transferred to an autoclave, and then 1.5 kg of propylene was inserted, followed by polymerization at 25 ° C. for 2 hours. The unreacted propylene was removed after the polymerization, and the powder taken out was washed three times with 2 l / hexane of 3 times to obtain 230 g of syndiotactic polypropylene as a portion insoluble in hexane. The intrinsic viscosity of the obtained powder measured at 135 ° C. in tetralin solution (hereinafter, referred to as
(abbreviated as η) was 1.48, and the syndiotactic pentad fraction was 0.918.

Comparative Example 1 Beforehand, 0.67 g of methylaluminoxane was put into a 5 l autoclave without polymerization in toluene, and propylene was added.
After charging 1.5 kg, a solution obtained by dissolving 5 mg of isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride in 10 ml of toluene was similarly introduced in four portions under stirring (however, the injection was performed under nitrogen pressure). Others were the same as in Example 1. 63 powder insoluble in hexane
g obtained. The obtained powder had η of 1.41 and a syndiotactic pentad fraction of 0.908.

Comparative Example 2 The same procedure as in Example 1 was carried out except that hexane was used instead of toluene as the solvent in the initial polymerization of propylene, whereby 142 g of a powder insoluble in hexane was obtained. The η of the obtained powder is 1.46, and the syndiotactic pentad fraction is
0.918. During the polymerization in hexane, 280 g of propylene was polymerized per 1 g of isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride.

Example 2 Polymerization was carried out in advance by using ethylbenzene in place of toluene and using 0.2 g of methylaluminoxane. In addition, during the bulk polymerization, the above slurry and propylene were charged, and then 0.43 g of methylaluminoxane was injected to perform polymerization. Was. 208 g of a powder insoluble in hexane was obtained. Η of the obtained powder
Was 1.38 and the syndiotactic pentad fraction was 0.920. During the polymerization in ethylbenzene, 310 g of propylene was polymerized per 1 g of isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride.

〔The invention's effect〕

By carrying out the method of the present invention, syndiotactic polypropylene can be obtained with high activity per catalyst, which is extremely valuable industrially.

[Brief description of the drawings]

FIG. 1 is a flow diagram to help understand the method of the present invention.

Claims (3)

(57) [Claims] (1) Isopropyl (cyclopentadienyl-1)
-Fluorenyl) hafnium dichloride and isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride in a method of polymerizing propylene using a catalyst comprising an aluminoxane and a transition metal catalyst component, a small amount of an aromatic hydrocarbon compound in advance A method for producing syndiotactic polypropylene, comprising contacting a transition metal catalyst component with an aluminoxane in the presence of propylene to polymerize propylene, and then polymerizing propylene using the slurry in the presence of liquid propylene. 2. The process according to claim 1, wherein the polymerization in the aromatic hydrocarbon compound is carried out until from 0.1 g to 10,000 g of propylene per 1 g of the transition metal catalyst component is polymerized. 3. A transition metal catalyst component comprising an aromatic hydrocarbon compound.
The method according to claim 1, wherein 10 to 100 ml of liquid propylene is used per 1 g, and 10 ml or more of liquid propylene is used per 1 ml of aromatic hydrocarbon compound.