JPH0778092B2 - Olefin Polymerization Method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for polymerizing olefins. More specifically, the present invention relates to a method for polymerizing or copolymerizing olefins using a novel Ziegler type catalyst system at a pressure of 200 kg / cm ² or more and a high temperature of 160 ° C. to 250 ° C. and a high pressure.

<Prior Art> A technique of polymerizing or copolymerizing an olefin in a molten state of a polymer under solvent-free, high-temperature and high-pressure using a Ziegler type catalyst is known as a “high pressure ion method”.

The high-pressure ionic polymerization method using a Ziegler type catalyst is known to have advantages such as a compact reactor and a large degree of freedom in selecting comonomer. Further, in such high temperature polymerization, it is easy to remove a large amount of heat of polymerization during the polymerization, and it is extremely advantageous in terms of a process since the polymer in a molten state can be used as it is even in granulation with a polymerization degree. Are known. The polymerization temperature is preferably as high as possible in consideration of the productivity of increasing the conversion rate of the olefin monomer into the polymer.

However, it is generally known that the polymerization activity of the catalyst decreases as the polymerization temperature increases. If the polymerization activity is low, there is concern about corrosion of equipment and equipment due to active halogens of metal halides such as titanium halide compounds and magnesium halides, and in terms of product quality, the catalyst obtained from the polymer obtained after polymerization is the catalyst. The residue needs to be removed. Therefore,
Polymerization activity per catalyst is high enough that a large amount of catalyst residue such as halogen does not remain in the product from the viewpoints of measures against equipment and equipment corrosion and simplification of manufacturing process without the need to remove catalyst residue. A catalyst system is desired.

Further, it is generally known that the molecular weight of the produced polymer decreases as the polymerization temperature increases, and particularly at a relatively high polymerization temperature, for example, 160 ° C. or higher, the molecular weight of the produced polymer cannot reach a sufficiently high region. was there. This problem becomes more remarkable when trying to produce a copolymer. This is because when ethylene and α-olefin are copolymerized, the chain transfer rate of α-olefin becomes higher than that of ethylene, and the molecular weight of the produced polymer does not become sufficiently high.

Therefore, a catalyst system which gives a polymer having a desired molecular weight, of course, has a high activity in a sufficiently high temperature range where the conversion rate to a polymer does not become low, and there has been a strong demand.

For this reason, individual improvements have been made to the high temperature Ziegler type catalyst. For example, regarding the method of controlling the molecular weight of the produced polymer in high temperature polymerization, a catalyst system using a mixture of diethylaluminum chloride and an alkoxy-containing organoaluminum compound or an alkylsiloxane derivative as a cocatalyst (JP-A-56-161407) and organomagnesium A catalyst system that uses a mixture of a compound, a halogen-free nickel compound, and an organoaluminum halogen compound as a cocatalyst (JP-A-59-166512), or an organoaluminum compound that contains a halogen group and has a Si-OR bond A catalyst system using a silicon compound as a cocatalyst has been reported (Japanese Patent Laid-Open No. 59-204605), and any catalyst system has a catalytic activity, a molecular weight of a polymer, an apparatus, a device, etc. It was still unsatisfactory in terms of corrosion.

<Problems to be Solved by the Invention> In such a current situation, the problem to be solved by the present invention is that the catalyst activity is sufficiently high so that the removal of the catalyst residue becomes unnecessary in a sufficiently high pressure and temperature range, and the apparatus and the device Another object of the present invention is to provide a method for polymerizing an olefin with a catalyst system which is less corrosive and has good controllability of the molecular weight of the produced polymer.

<Means for Solving Problems> The present invention has a pressure of 200 kg / cm ² or more and 160 ° C. or more, 250 ° C.
A method for polymerizing an olefin, which comprises polymerizing ethylene using a catalyst system comprising the following components A, B and C at the following temperatures, or copolymerizing ethylene with at least one α-olefin: It is a thing.

Component A: Trialkylaluminum Component B: General formula Solid catalyst component represented by the formula (wherein n is 1 ≦ n ≦ 6) Component C: Silicon compound represented by the general formula Si (OR) ₄ (wherein R is a carbon-hydrogen group containing 1 to 20 carbon atoms) The use of the present catalyst system achieves the above objectives.

Hereinafter, the present invention will be specifically described.

(1) Component A Component A is trialkylaluminum. Specifically, the following compounds may be mentioned as examples. For example, triethyl aluminum, tripropyl aluminum, tributyl aluminum, tri-iso-butyl aluminum, trihexyl aluminum, trioctyl aluminum and the like. These trialkylaluminums may be used alone or in combination of two or more kinds.

Of these trialkylaluminums, triethylaluminum is preferred.

(2) Component B Component B is a general formula Is a solid catalyst component (where n is 1 ≦ n ≦ 6).

Component B is generally a solid composition obtained by pulverizing a eutectic of titanium trichloride and aluminum chloride and magnesium chloride, and its specific surface area is preferably 1 m ² / g or more, more preferably 5 m ² / g or more, magnesium / Titanium (atomic ratio)
Is 1 to 6. If the magnesium / titanium (atomic ratio) is too low, the polymerization activity will be low, and if the magnesium / titanium (atomic ratio) is too high, the molecular weight of the produced polymer will not be sufficiently high.

(3) Component C Component C is a silicon compound represented by the general formula Si (OR) ₄ (R represents a hydrocarbon group containing 1 to 20 carbon atoms). R is preferably selected from alkyl, cycloalkyl, aryl and alkenyl groups. Specifically, the following compounds can be exemplified. For example, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane,
Examples thereof include tetra-iso-propoxysilane, tetrabutoxysilane, tetracyclohexoxysilane, and tetraphenoxysilane. These silicon compounds may be used alone or in combination of two or more.

Of these silicon compounds, tetraethoxysilane is preferably used.

(4) The polymerization conditions in the present invention are that the temperature is 160 ° C to 250 ° C,
Preferably 180 ℃ ~ 250 ℃, more preferably 200 ~ 150 ℃,
Pressure 200~3,500kg / cm ^2, preferably 600~1,800kg / cm ²
The polymerization can be carried out in a batch system or a continuous system, but the continuous system is preferred.

As the reactor, a stirred tank reactor or a tubular reactor is used. The polymerization is carried out in a single reaction zone, but one reactor may be divided into a plurality of reaction zones, or a plurality of reactors may be continuously carried out in series or in parallel. When using a plurality of reactors, any combination of tank type-tank type or tank type-tube type may be used. In the method of polymerizing in a plurality of reaction zones or a plurality of reactors, it is also possible to produce polymers having different characteristics by changing the temperature, pressure and gas composition for each reaction zone.

The catalyst is fed to the reactor by a high pressure pump as a fine dispersion in a suitable inert solvent. In the polymerization under high pressure as in the present invention, the catalyst is injected into the high pressure portion by a pump, so that the particle size must be small and the dispersibility in the solvent must be good. In general, the following methods can be mentioned as a method for making the catalyst particles finer. That is, (a) milling in a ball mill or the like, (b) unbranched α-containing at least 6 carbon atoms in the presence of a solid catalyst component and a trialkylaluminum, as described in British Patent 979,123. There are methods such as prepolymerization of olefins.

Suitable inert solvents include, for example, white spirit, hydrocarbon oils, pentane, hexane, heptane, octane, toluene, higher branched chain saturated aliphatic hydrocarbons, isobutene oligomers, oligomers such as 1-butene oligomers, and mixtures thereof. Can be given. It is necessary to handle the catalyst dispersion under an atmosphere of an inert gas such as nitrogen or argon so as not to come into contact with water and air.

In the present invention, the silicon compound of Component C can be added to the polymerization system by any method. The silicon compound of component C can be added alone to the polymerization system, or used by mixing with a solid catalyst component (component B) containing a transition metal or a trialkylaluminum component (component A) before the initiation of polymerization. It may be added all at once at the start of the polymerization, or may be added continuously or dividedly during the polymerization period. In carrying out the method of the present invention, component C
The amount of silicon compound can vary within wide limits. The amount of the silicon compound as the component C is 0.005 to 5 mol, preferably 0.01 to 1 mol, and more preferably 0.05 to 0.5 mol, relative to 1 mol of the trialkylaluminum.

Also, trialkylaluminum and Ti contained in component B
Is used in a molar ratio of 1 to 200, preferably 2 to 100, more preferably 3 to 50.

(5) The α-olefin used in the present invention has 3 carbon atoms.
.About.20, preferably 3 to 10, .alpha.-olefins. Examples thereof include propylene, butene-1,4-methylpentene-1, hexene-1, octene-1, vinylcyclohexane and the like.

And the present invention relates to ethylene homopolymers or ethylene containing at least 80 mol% ethylene and other α-olefins, especially propylene, butene-1,4-methylpentene-1, hexene-1, octene-. Α such as 1
-It can be effectively applied to the production of a copolymer with an olefin.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention should not be limited thereto.

The properties of the polymers in the examples were measured by the following methods.

That is, the density is JIS K-6760, the melt index (MI) is
Obtained in accordance with ASTM 1238-57T.

Example 1 (1) Preparation of solid catalyst component Commercially available anhydrous magnesium chloride 100 g, manufactured by Toho Titanium Co., Ltd.
100 g of TAC-131 (TiCl ₃ .1 / 3AlCl ₃ ) was ball milled for 40 hours to obtain a solid catalyst component. Analysis of this powder
It contained Ti 10.9%, Al 1.3%, Cl 74.6%, and Mg 12.0% (all in weight%).

(2) Preparation of catalyst dispersion Put 7 liters of heptane into a 10 liter tank that has been sufficiently replaced with nitrogen,
Further, 14 millimoles of triethylaluminum, the above (1)
7 g of the solid catalyst component obtained in step 1 was added. Then hexene-1
Was added and the stirring was continued to give a viscous solid catalyst dispersion. On the other hand, 7 l of heptane was placed in another 10 l tank which had been sufficiently replaced with nitrogen, and 140 mmol of triethylaluminum and 14 mmol of tetraethoxysilane were further added to obtain a cocatalyst solution.

(3) Polymerization of ethylene Under the reaction conditions shown in Table 1, ethylene and butene-1 were copolymerized in an autoclave type continuous reactor equipped with a stirrer and having an internal volume of 1. As the catalyst, the co-catalyst liquid prepared in (2) above was used as the components A and C, and the solid catalyst dispersion prepared in (2) above was used as the component B. Both were contacted with the autoclave immediately before they were supplied to the autoclave. It was fed continuously.

As a result of the polymerization, 114,000 g of a polymer was obtained per 1 g of the transition metal. The polymer thus obtained had an MI of 0.91 (g / 10 minutes) and a density of 0.91.
It was 9.

Comparative Example A Polymerization was performed in the same manner as in Example 1 except that diethylaluminum chloride was used as the component A in Example 1. The results of the polymerization are shown in Table 1, and the amount of the catalyst residue is shown in Table 2. As is clear from Table 2, the use of halogen-containing organoaluminum as the component A causes a large amount of halogen to be contained in the polymer. This is not preferable because it causes corrosion of the equipment and devices.

Comparative Example B Polymerization was carried out in the same manner as in Example 1 except that tetraethoxysilane (component C) was not used. The results are shown in Table 1. As is clear from Table 1, a polymer having a desired molecular weight cannot be obtained without using tetraethoxysilane.

Comparative Example C Polymerization was carried out in the same manner as in Example 1 except that the polymerization temperature was changed to 280 ° C. The results are shown in Table 1.
As is apparent from Table 1, when the polymerization temperature is too high, the polymer having the desired molecular weight cannot be obtained even if the component C is used.

Comparative Example D Polymerization was carried out in the same manner as in Example 1 except that TAC-131 was used as the component B in Example 1. The results are shown in Table 1. As is clear from Table 1, the polymerization activity is remarkably low in the catalyst system containing no magnesium chloride.

Comparative Example E (1) Preparation of solid catalyst component Commercial anhydrous magnesium chloride 70 g, Toho Titanium TAC
10 g of -131 (TiCl ₃ · 1 / 3AlCl ₃ ) was ball milled for 40 hours to obtain a solid catalyst component. When this powder was analyzed, it was Ti 2.
It contained 9%, Mg22.4%, Al1.7%, Cl72.7% (all are weight%).

(2) Preparation of Catalyst Dispersion Liquid was prepared in the same manner as in Example 1 (2) except that the solid catalyst component obtained in (1) above was used.

(3) Polymerization of ethylene Example 1 except that the catalyst dispersion obtained in (2) above was used.
Polymerization was carried out in the same manner as in. The results are shown in Table 1. As is apparent from Table 1, when a solid catalyst component (Mg / Ti> 6) containing a large amount of magnesium chloride is used, even if the component C is used, a polymer having a desired molecular weight cannot be obtained.

Example 2 Copolymerization of ethylene and hexene-1 was carried out using the same catalyst system as in Example 1. The polymerization results are shown in Table 1.

The use of component C gives the desired molecular weight polymer.

Example 3 Copolymerization of ethylene and 4-methylpentene-1 was carried out using the same catalyst system as in Example 1. The polymerization results are shown in Table 1.

The use of component C gives the desired molecular weight polymer.

Example 4 Example 1 was repeated except that the supply amount of butene-1 was changed and tetrabutoxysilane was used as the component C.
Polymerization was carried out in the same manner as in. The polymerization results are shown in Table 1. The use of component C gives the desired molecular weight polymer.

<Inventive effect> In the olefin polymerization method of the present invention, at a pressure of 200 kg / cm ² or more and at a polymerization temperature of 160 ° C. or more and 250 ° C. or less, the catalyst content in the polymer produced by the high catalytic activity per transition metal is contained. Since the amount is small, the catalyst removal step can be omitted.
Further, a polymer having a desired molecular weight can be produced at a certain limited polymerization temperature without lowering productivity. Furthermore, the use of halogen-free trialkylaluminum eliminates corrosion of the polymerization tank and is industrially very advantageous.

[Brief description of drawings]

FIG. 1 is a flow chart for facilitating the understanding of the present invention. This flowchart is a representative example of the embodiment of the present invention, and the present invention is not limited to this.

Claims (1)

[Claims] 1. A pressure of 200 kg / cm ² or more and 160 ° C. or more, 25
Polymerization of ethylene using a catalyst system consisting of the following components A, B and C at a polymerization temperature of 0 ° C. or lower, or a copolymerization process of ethylene and at least one α-olefin. . Component A Trialkylaluminum Component B General formula Solid catalyst component represented by the formula (where n is 1 ≦ n ≦ 6) Component C Silicon compound represented by the general formula Si (OR) ₄ (wherein R represents a carbon-hydrogen group containing 1 to 20 carbon atoms) )