JPH0618823B2 - Heterogeneous polymerization of olefins - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention is a so-called slurry polymerization method in which olefin is heterogeneously polymerized in a solvent in the presence of a catalyst. And a method for stably producing polyolefin.

[Problems to be solved by the invention]

As a method for producing polyolefin by polymerizing or copolymerizing olefin, so-called slurry polymerization in which a solid catalyst is suspended in a solvent to perform polymerization is generally adopted.
However, in the case of this slurry polymerization, the low molecular weight polymer produced as a by-product in the polymerization reaction is easily dissolved in the solvent, and adhesion to the wall of the polymerization vessel occurs, so that the heat transfer coefficient decreases and long-term continuous stable operation becomes difficult. It is usually In particular, in the case of producing a low-density copolymer by copolymerization with other olefins, adhesion to the vessel wall as described above, deterioration of the heat transfer coefficient is likely to occur, long-term stable operation becomes impossible, or significantly. Reduce productivity.

As a method for preventing such a polymer from adhering to the vessel wall, there is a method of keeping the slurry concentration low, but this is not preferable because it lowers the productivity. Although many methods have been proposed in which the catalyst is pretreated with a small amount of olefin in advance, they are not always satisfactory.

[Means for solving problems]

As a result of intensive studies to solve the above problems, the present inventors have shown that when olefin is polymerized by a slurry polymerization method, the presence of chlorofluorocarbons in the polymerization system causes the wall of the polymer to grow. The present invention has been achieved by finding that adhesion is prevented.

That is, the gist of the present invention is a method of heterogeneously polymerizing an olefin in a solvent in the presence of a catalyst to produce a crystalline olefin polymer, wherein chlorofluorocarbons are present in the polymerization system. In the heterogeneous polymerization method.

Further, to explain the present invention in detail, the present invention is particularly effective for copolymers in which a low molecular weight component is easily produced, and the production of a low density polymer or a soft polymer, which has been difficult to produce by the conventional method, is conducted by the present invention. Can be easily implemented.

For example, polyethylene having a density of 0.90 to 0.94 g / cm ³ and polypropylene having an ethylene content of 4 to 8% can be produced without lowering the productivity.

The olefins used in the present invention include ethylene, propylene, butene-1, pentene-1, hexene-1,
Octene-1,4-methylpentene-1,3-methylbutene-1 and the like can be mentioned. The above olefins may be homopolymerized or may be mixed and copolymerized.

As the polymerization solvent, a hydrocarbon solvent usually used in slurry polymerization is used. Specifically, aliphatic hydrocarbon solvents such as propane, isobutane, normal butane, normal pentane, normal hexane, normal octane, etc., alicyclic hydrocarbon solvents such as cyclopentane, cyclohexane, etc., or aromatic hydrocarbons, for example. , Benzene, toluene, xylene, etc. are used alone or in admixture of two or more. Also, propylene, butene-
Olefins such as 1, hexene-1 can also be used as a solvent.

As the polymerization catalyst, a known olefin polymerization catalyst is applied. For example, transition metal compounds of Groups 4 to 6 of the Periodic Table such as titanium, vanadine, and zircon, and Periodic Tables 1 to 3 of the Periodic Table.
So-called Ziegler-based catalysts consisting of group-organic organometallic compounds, so-called Ziegler-Natta-based catalysts containing titanium trichloride or titanium trichloride / metal halide eutectic and organoaluminum compounds as main components, and so-called Phillips catalysts (silica). Typical examples thereof are alumina, etc. carrying chromium oxide) and standard type catalysts (γ-alumina carrying molybdenum oxide).

The polymerization reaction is usually carried out at room temperature to 100 ° C. and the polymerization pressure is at normal pressure to 100 atm.

The chlorofluorocarbons used in the present invention are compounds in which H or all or part of H in the molecule of the hydrocarbon derivative is substituted with F and C1. Specifically, monochlorodifluoromethane, trichloromonofluoromethane, dichlorodifluoromethane, monochlorotrifluoromethane, tetrachlorodifluoroethane, trichlorotrifluoroethane, dichlorotetrafluoroethane and the like.

The amount of the above fluorinated carbon compound added is 0.01 to 5% by weight, preferably 0.05 to 1% by weight, based on the solvent in the polymerization reactor.
Is. If the added amount is too small, the effect of preventing the polymer from adhering to the vessel wall is insufficient, and if the added amount is too large, the polymerization activity is reduced, which is not preferable.

The addition method is not particularly limited, but it may be added in the solvent in advance, or may be added during the polymerization.

〔Example〕

Next, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

In the following examples, the polymerization activity K of the catalyst is K =
It was expressed by (g polymer) / (g solid catalyst). (Hr). (Kg / cm ² olefin pressure).

Melt index (MI) is 19 based on JIS K-6760
The value is measured at 0 ° C. under a load of 2.16 kg, and the unit is g / 10 minutes. The density (g / cc) was measured according to JIS K6760.

The normal hexane soluble component was measured by extracting the polymer powder with a Soxhlet extractor for 2 hours with boiling normal hexane.

Example-1 (A) Preparation of catalyst component 113 g of magnesium diethoxide, 150 g of tri-n-butoxymonochlorotitanium and 37 g of n-butanol
And were mixed at 130 ° C. for 6 hours to homogenize. Then 60
The temperature was lowered to ℃ and normal hexane 3.75 was added.

Next, 457 g of ethylaluminum sesquichloride was added dropwise, and stirring was continued at 60 ° C. for 1 hour. By washing the formed precipitate with n-hexane, a brown catalyst component 2
10 g were obtained. A part of the obtained solid was dried and made into powder, and as a result of analysis, Mg was 10.0% by weight and Ti was 9.8% by weight.
Was included.

(B) Polymerization of ethylene Using the solid catalyst component obtained in (A) above, the internal volume is 500
In the polymerization tank with a jacket, continuous polymerization of ethylene-butene-1 copolymerization was carried out with a normal hexane solvent at a liquid level of 300.

To the polymerization tank, 1.2 g / hr of the above solid catalyst component, 2.3 g / hr of diethylaluminum chloride, and purified normal hexane 7
5kg / hr, trichlorotrifluoroethane (CCl ₂ F ・ CClF ₂ )
75 g / hr, ethylene 25 kg / hr, butene-15 kg / hr,
Hydrogen is continuously supplied at a rate of 5 g / hr to obtain a polymerization temperature of 60 ° C.,
Continuous polymerization was carried out for 20 days at a total pressure of 5 kg / cm ² -G and an average residence time of 2 hours.

The average polymerization activity K during this period was 2700 (g-polymer / g
-Catalyst · hr · ethylene pressure) and M of the obtained polymer
I was 1.5 (g / 10 minutes), the density was 0.940 (g / cm ³ ), and the boiling normal hexane extract was 5.2% by weight.

The heat removal by water flow through the jacket is extremely stable, and the overall heat transfer coefficient (Uo) 380 (Kcal / m ² · hr
For example, the overall heat transfer coefficient (Uf) immediately before the end of polymerization is 350 (Kca
l / m ² · hr · deg), during which the rate of decrease (1-Uf / Uo) is
It was 0.39% / day. When the reactor was opened and inspected after the operation was completed, almost no adhesion was found on the vessel wall.

Comparative Example-1 Ethylene-butene-1 was prepared in the same manner as in Example-1, except that trichlorotrifluoroethane was not supplied.
Was copolymerized.

The polymerization activity K during operation was 3050 (g polymer / g catalyst.hr.
・ Ethylene pressure), MI of the product is 1.2 (g / 10min), density is 0.940 (g / cm ³ ) Normal hexane extract is 5.5% by weight
It was.

Regarding the decrease in the overall heat transfer coefficient of the polymerization tank, the overall heat transfer coefficient (Uo) of the heat transfer surface immediately after the start of polymerization was 420 (Kcal / m ² hr deg), but it gradually decreased during operation. On the 10th day, 300 (Kcal / m ² ·
(Hr / deg) and finally the polymerization was stopped. The average reduction rate (1-Uf / Uo) during this period was 2.4% / day.

After completion of the reaction, the reactor was opened and inspected, and wax-like adhesion was observed on the entire wall of the reactor.

From these results, long-term operation was judged to be difficult.

〔The invention's effect〕

 According to the method of the present invention, the polymer is prevented from adhering to the vessel wall.

[Brief description of drawings]

FIG. 1 is a flow chart showing one embodiment of the catalyst used in the present invention.

Claims (1)

[Claims] 1. A method for producing a crystalline olefin polymer by heterogeneously polymerizing an olefin in a solvent in the presence of a catalyst, wherein chlorofluorocarbons are present in the polymerization system. Polymerization method.