JPH03200808A - Production of polyethylene - Google Patents

Abstract

PURPOSE:To obtain a polymer not requiring any deashing step in a very high polymerization activity by (co)polymerizing ethylene at a reaction temperature equal to or higher than the m.p. of the polymer in the presence of a catalyst comprising a specified transition metal compound and a specified organometallic compound. CONSTITUTION:A process for polymerizing ethylene or copolymerizing ethylene with at least one alpha-olefin at a reaction temperature equal to or higher than the m.p. of the polymer in the presence of a catalyst comprising a transition metal compound and an organometallic compound, wherein the catalyst system comprises a solid catalyst (A) obtained by treating a solid component, obtained by copulverizing a magnesium dihalide and a titanium trihalide, with a titanium halide and in a suspended state and a mixture (B) comprising at least two members selected from the group consisting of an organoaluminum compound of formula I (wherein R<1> is 1-20C alkyl), an organoaluminum compound of formula II (wherein R<2> is 1-20 C alkyl; X<1> is halogen; and 0<j<=2) and an organoaluminum compound of formula III (wherein R<3> and R<4> are each 1-20C alkyl; and 1<=k<=2) or an aluminoxane.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing polyethylene using a novel catalyst. More specifically, the present invention relates to a method for producing polyethylene, which comprises polymerizing ethylene or copolymerizing ethylene and α-olefin using a novel catalyst with high catalytic activity at a temperature equal to or higher than the melting point of polyethylene.

In general, ethylene polymers and ethylene-α-olefin copolymers polymerized by Ziegler type catalysts have a wide range of density, usually from 0.880 to 0.975 g/cm', and are used for a wide range of applications such as films and molded products. It is being said.

[Conventional technology]

Solution polymerization and high-temperature and high-pressure polymerization are known as methods for polymerizing ethylene using a Ziegler type catalyst at a temperature equal to or higher than the melting point of polyethylene. - Generally, in a solution polymerization method carried out in an inert solvent, the polymerization temperature is preferably higher in view of lowering the viscosity of the solution and facilitating removal of polymerization heat. Similarly, in the high-temperature, high-pressure method, the greater the temperature difference between the polymerization temperature and the feedstock, the better the ethylene conversion rate, and therefore the higher the polymerization temperature, the greater the economic benefit. On the other hand, in polymerization in these high temperature ranges, catalyst activity and activity sustainability generally decrease as the polymerization temperature increases. When the catalyst activity is low, the amount of catalyst residue in the polymer increases, which tends to cause corrosion of process equipment, coloring of the polymer, and gel formation. Conventionally, many proposals have been made as catalysts that can be used in high-temperature polymerization. For example, a catalyst system that combines a titanium halide, an alkyl aluminum compound containing a halogen group, and an organomagnesium compound is
Presented in 1372. However, it cannot be said that the catalytic activity of this catalyst system is satisfactory, and further improvement of the catalytic activity is desired.

Further, the basic physical properties of the copolymer obtained by copolymerizing ethylene and α-olefin are determined by the amount of comonomer introduced into the ethylene chain and its distribution. That is, the number and distribution of short chain branches greatly influence the basic properties of the polymer, such as crystallinity, crystallization rate, spherulite structure, and melting point. In turn, from the point of view of practical physical properties, it will affect many aspects such as environmental stress resistance, film strength, flexibility, and moldability.

From the above, controlling the number and distribution of short chain branches in a copolymer is very important for improving practical physical properties.

The degree of branching distribution in copolymers is thought to be greatly influenced by factors such as copolymerization reactivity with comonomers and ease of chain transfer by molecular weight regulators (particularly hydrogen); Short-chain branching distribution of copolymers of ethylene and α-olefins obtained by catalyst systems such as the organoaluminum compound (e.g. trialkylaluminium)-titanium trichloride system and the organoaluminum compound-titanium tetrachloride system. However, it was not possible to significantly change the basic properties of the polymer, such as melting point and crystallization rate, because it was not clear how to control it.

Furthermore, the reactivity of the comonomer in copolymerization is thought to be closely related to the distribution of the degree of branching, but especially in the case of copolymerization with α-olefins having 4 or more carbon atoms, the degree of conversion of the comonomer varies. occupies a large proportion of manufacturing costs.

However, when the performance of the catalyst system of the prior art as a copolymerization catalyst of ethylene and α-olefin was investigated, it was found that the controllability of the branching degree distribution of the obtained polymer and the reactivity with the comonomer were satisfactory. Therefore, there was a strong desire to develop a method to control these copolymerization performances.

[Problem to be solved by the invention]

The purpose of the present invention is to perform polymerization in a temperature range higher than the melting point of polyethylene, that is, in solution polymerization or high temperature and high pressure polymerization.
The object of the present invention is to provide a catalyst system that is so highly active that it does not require a catalyst removal step, has excellent activity persistence and comonomer reactivity, and can control the branching degree distribution of the resulting polyethylene.

[Means to solve the problem]

The gist of the present invention is to polymerize ethylene at a reaction temperature higher than the melting point of the polymer in the presence of a catalyst consisting of a transition metal compound and an organometallic compound, or to polymerize ethylene with at least IFli.
In copolymerizing the α-olefin, as component (A), a solid component obtained by co-pulverizing (I) magnesium dihalide and (II) titanium trihalide is further added in a suspended state to (m) A solid catalyst component obtained by treatment with a halogenated titanium compound; and (a) as the component (B), represented by the general formula AIR', (wherein R1 represents an alkyl group having 1 to 20 carbon atoms). (b) General formula A I R2HX'! -1 (in the formula, R2
represents an alkyl group having 1 to 20 carbon atoms,
I represents a halogen atom, j represents a number Q<j≦2); and (C) general formula A I R'(OR' ) 5-k
(In the formula, R3 and R4 represent an alkyl group having 1 to 20 carbon atoms, and k represents a number of 1≦k≦2.) Or an aluminoxane, A method for producing polyethylene characterized by using a catalyst system consisting of a mixture of at least two types.

[Effect]

The above-mentioned magnesium dihalide (I), which is a reactant used in the present invention, is an anhydrous one, and representative examples include magnesium chloride, magnesium bromide, and magnesium iodide, with magnesium chloride being particularly preferred.

Examples of the titanium trihalide which is the reactant in (II) include titanium trifluoride, titanium trichloride, titanium tribromide, and titanium triiodide.

Among them, titanium trichloride is preferred. Titanium trichloride may be obtained by reducing titanium tetrachloride with hydrogen or aluminum, or by reducing it with an organoaluminum compound such as diethylaluminum chloride, and may also be prepared by adding 1 mol of AJ C13.

Further, as the halogenated titanium compound which is the reactant of the above (III), a titanium compound represented by the general formula T i (OR') a X 2a-m is used. In the general formula, R5 represents a hydrocarbon group having 1 to 20 carbon atoms, and
2 represents a halogen atom, and n represents a number satisfying O≦n and 4. R5 is a straight or branched alkyl group, cycloalkyl group, or arylalkyl group.

Preferably it is selected from aryl and alkylaryl groups.

The above halogenated titanium compounds can be used alone or as a mixture of two or more. Specific examples of halogenated titanium compounds include titanium tetrachloride, ethoxytitanium trichloride, propoxytitanium trichloride, butoxytitanium trichloride, phenoxytitanium trichloride, jetoxytitanium dichloride, triethoxytitanium chloride, etc. . Among them, titanium tetrachloride is preferably used.

In the present invention, the co-pulverization of reactants (1) and (II) is carried out using 2
The components may be coexisting at the same time or may be carried out in two stages without any problem. The co-milling process is usually carried out in an inert gas atmosphere using a ball mill, vibration mill or impact mill.

The optimum conditions for co-grinding are the type of balls and the filling rate.

It varies depending on the rotation speed, grinding temperature, grinding time, etc.
Such conditions can be easily determined through experiments by those skilled in the art.

Examples of solvents for treating the solid component after co-pulverization with the halogenated titanium compound of the reactant (I) include chloroform, carbon tetrachloride, 1,1-dichloroethane,
Examples include 1,2-dichloroethane, 1,1°1-trichloroethane, 1,1,2,2-tetrachloroethane, 1-chloropropane, tert-butyl chloride, and monochlorobenzene. The treatment of the solid component and the reactant (III) is usually carried out at a temperature below the boiling point of the solvent.

The amount of each reactant constituting the catalyst component (A) to be used is arbitrary as long as the effect of the present invention is observed. preferable. In addition, the amount of the halogenated titanium compound used as the reactant (■) is 0.02 to 0.02 to 1 mole of magnesium dihalide as the reactant (I).
100 mol, preferably in the range of 0.05 to 50 mol. Treatment with a halogenated titanium compound in a suspended state t2 as the reactant (m) is effective in improving polymerization activity and copolymerizability.

The catalyst component (B) used in the present invention includes (
a) an organoaluminum compound represented by the general formula AIR', in which R1 represents an alkyl group having 1 to 20 carbon atoms; (b) an organoaluminum compound represented by the general formula A I R2HX" s-+
(In the formula, R2 represents an alkyl group having 1 to 20 carbon atoms, X' represents a halogen atom, and j represents O<j
≦2); and (C)-general formula A I R3 (OR' ) s-*
(In the formula, R3 and R4 represent an alkyl group having 1 to 20 carbon atoms, and k represents a number of 1≦k≦2.)
Examples include a mixture of at least two of the organoaluminum compounds represented by the following, or aluminoxane.

Specific examples of the organoaluminum compound represented by the general formula AIR' in (a) above include trimethylaluminum, triethylaluminum, triisopropylaluminium, triisobutylaluminum, trihexylaluminum, trioctylaluminum, tridecylaluminum, etc. Examples include trialkyl aluminum.

Specific examples of the organoaluminum compound represented by the general formula AIR" I
Ethylaluminum dichloride, diethylaluminum monobromide.

Examples include alkyl aluminum halides such as diisopropyl aluminum monobromide.

General formula A I R' * (OR') of the above (c)
Specific examples of organoaluminum compounds represented by s-* include alkyl aluminum alkoxides such as dimethylaluminum ethoxide, diethylaluminum ethoxide, diethylaluminium propoxide, diethylaluminium butoxide, diethylaluminum phenoxide, and ethylaluminum jetoxide. etc. can be mentioned. Further, as the aluminoxane (C) above, an aluminoxane compound in which two or more aluminum atoms are bonded via an oxygen atom or a nitrogen atom, for example, a multimer such as tetramethylaluminoxane or polymethylaluminoxane, etc. can also be used.

The total amount of the mixture of at least two of the organoaluminum compounds (a), (b), and (C) used as the above component (B) is based on 1 gram atom of titanium contained in the catalyst component (A). 1 to 1000 mol, preferably 1
~100 moles. Organoaluminium compounds (
a), (b) and (C) can be combined in any way, but (b)/ (a) -0,1 to 0.9 and or (c)/ (a) -0,1 It is preferable to set it in the range of ~0.9. By forming a mixture of two or more types of component (B), the effect of improving polymerization activity and copolymerizability is brought about.

The polymerization of the present invention is a homopolymerization of ethylene or a copolymerization of ethylene and an α-olefin of at least IFJ.

The α-olefin used for copolymerization with ethylene preferably has 3 to 20 carbon atoms, and specific examples include propylene, 1-butene, 1-hexene, and 4-methyl-1-pentene.

1-octene, 1-decene, etc. and mixtures thereof are used.

Polymerization of ethylene is carried out at a temperature higher than the melting point of the resulting polymer, preferably 1
It is carried out at a temperature range of 30 to 300°C, and an inert solvent or the monomer itself is used as the polymerization medium.

In solution polymerization using an inert solvent, hexane, heptane, octane, nonane, decane,
Aliphatic hydrocarbons such as undecane and dodecane and mixtures thereof, aromatic hydrocarbons such as benzene and toluene, and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane are used. Polymerization pressure is 1 to 200 kX/cJ,
Preferably it is 10 to 50 kg/eJ, and the residence time is in the range of 10 minutes to 6 hours, preferably 20 minutes to 3 hours.

In addition, in high-temperature, high-pressure polymerization in which the monomer itself is used as the polymerization medium, a high-pressure radical polymerization device for ethylene can generally be used, and the polymerization pressure is 200 to 2500 kg/c.
d, preferably 400 to 1500 kg/cd, and residence time 5 to 600 seconds, preferably 10 to 150 seconds.

Furthermore, in the present invention, the molecular weight of the polymer can be controlled by adjusting the reaction temperature, but it can be easily controlled by the presence of hydrogen in the polymerization zone.

The amount of hydrogen needs to be appropriately adjusted depending on the polymerization conditions and the desired molecular weight of the ethylene polymer.

That is what we are doing. Therefore, it has a relatively long active life even at high temperatures.

The third effect of the present invention is that the width of the branching degree distribution of the resulting copolymer can be controlled. Therefore, the basic properties of the copolymer, such as crystallinity, crystallization rate, crystal structure, etc., can be adjusted depending on the application.

The fourth effect of the present invention is that α-olefin (comonomer)
Since the copolymerizability of the comonomer is good, the polymerization conversion rate of the comonomer is higher than that of other catalyst systems.

(A small amount of α-olefin to be copolymerized can be used.) [Effects of the invention] First, the effects of the invention are that the polymerization activity per transition metal and per solid catalyst is extremely high, and the desorption for the purpose of catalyst removal is It is possible to obtain a polymer that does not require an ash process. Since it is highly active, there is no need to worry about coloring or odor of the product, and there is no need to purify the polymer, making it extremely economical.

The second effect of the present invention is that the catalyst has excellent thermal stability [Examples] The present invention will be illustrated below by examples, but the present invention is not limited in any way by these examples unless the gist of the invention is exceeded. isn't it.

In the examples, MI represents melt index, and JIS
Based on K-6760, 190℃, load 2.16k
It was measured under the conditions of g. Density is JIS
Measured according to K-6760. Polymerization activity is the polymer production ffi (kg) per 1 g of solid catalyst component (A).
, and the amount of polymer produced (kg) per gram of transition metal component in the solid catalyst component (A).

The number of short chain branches was measured using a Fourier transform infrared spectrophotometer (FT-I
R) was determined from the peak derived from the methyl group appearing around 1378 cm-''.

The short chain branching degree distribution is based on glass beads (diameter approximately 0.1 mmφ
) packed column (3/8 inch outside diameter x 10011I)
11) was coated with a portion of a solution prepared by dissolving 10 g of polymer in 20 ml of orthodichlorobenzene, and then the column temperature was continuously increased, starting with those with low crystallinity or those with many methyl branches. Measurements were made using the TREF method, in which the eluate was sequentially eluted and the eluate was introduced into an infrared detector to obtain a methyl branch distribution (crystalline distribution) curve.

Example 1 [Preparation of solid catalyst component (A)] In a stainless steel pot with an internal volume of 420 ml containing 1.2 kg of stainless steel poles with a diameter of 4 mm, anhydrous magnesium chloride (commercially available anhydrous magnesium chloride was added in advance to 400 ml).
10.3 g (vacuum dried at ℃ for 2 hours) and 8.6 g of titanium trichloride (TiCρ, 1/3 AD C11m) obtained by reducing titanium tetrachloride with metal aluminum.
were sealed under a nitrogen atmosphere and co-milled for 12 hours in a vibrating mill. 5.0 g of the solid component obtained after pulverization was taken out, and 57 ml of titanium tetrachloride, 57 ml of 1,2-dichloroethane
The reaction was carried out at 90° C. for 2 hours in a heptane solution containing m1. After the reaction, hexane was added to the product, and the product was thoroughly washed until no liberated titanium compound was detected to obtain a solid catalyst component (A).

1.0 g of the obtained solid catalyst component (A) has 10 to 1 carbon atoms.
A catalyst slurry was prepared by dispersing No. 1 in 100 ml of a solvent (IF-1620, manufactured by Idemitsu Petroleum Science Co., Ltd.) containing isoparaffin as a main component.

[Copolymerization of ethylene and α-olefin] A stainless steel autoclave with an internal volume of 1 p and equipped with an induction stirrer was purged with nitrogen, 600 ml of IP-1620 and 20 ml of 1-butene were added, and the temperature was raised to 180° C. with stirring. The vapor pressure of the solvent and 1-butene in the system is 2.6 kg/
cd G, but with ethylene at a total pressure of 22, 6 k
g/cJ G
Then, a mixture of 0.07 n+mol of triethylaluminum and 0.071 mol of diethylaluminum chloride was added to start polymerization. When ethylene was continuously introduced and polymerization was carried out for 20 minutes while keeping the total pressure constant,
101 g of polymer was obtained. Polymerization activity per catalyst is 10
．． It was 1 kg/g catalyst. The activity per transition metal component was equivalent to 155 kg/g Ti. Ml is 2.3g/
10 minutes, density is 0. It was 917 g/cm'.

Further, the number of ethyl branches was 18 per 100OC. Further, when the short chain branching degree distribution of the produced polymer was determined by the TREF method, it showed a broad distribution curve in the elution temperature range of 30°C to 110°C.

Examples 2 to 6 Same as Example 1 except that the solid catalyst component (A) obtained in Example 1 was used and the type of organoaluminum compound used as the catalyst component (B) was changed as shown in Table 1. Copolymerization of ethylene and α-olefin was carried out under similar conditions.

The results are shown in Table 1, and the short chain branching degree distribution of the obtained polymer by the TREF method showed a broad distribution curve in the elution temperature range of 30°C to 100°C, almost the same as in Example 1.

Examples 7 to 9 The solid catalyst component (A) obtained in Example 1 was used, and in Examples 7 and 8, the ratio of the organoaluminum compound of the catalyst component (B) used in Example 1 was In Example 9, copolymerization of ethylene and α-olefin was carried out under the same conditions as in Example 1, except that the ratio of the organoaluminum compound of the catalyst component (B) used in Example 6 was changed as shown in Table 1. was carried out. The results are shown in Table 1, and the short chain branching degree distribution of the polymer obtained in Example 7.8 by the TREF method was within the elution temperature range of 40°C to 100°C.
Although the proportion around 5° C. was slightly lower than that in Example 1, a broad distribution curve was shown.

Further, the short chain branching degree distribution of the polymer obtained in the example by the TREF method showed a broad distribution curve in the elution temperature range of 30°C to 100°C.

Comparative Example 1 Anhydrous magnesium chloride (commercially available anhydrous magnesium chloride) was added in advance to a stainless steel pot with an internal volume of 420 ml containing 1.2 kg of stainless steel poles with a diameter of 4 mmφ.
and titanium trichloride obtained by reducing titanium tetrachloride with metallic aluminum (T i Cjll 3 ・l/3 All Cl3
s) 8.6 g were sealed under nitrogen atmosphere and co-milled in a vibrating mill for 12 hours. 1.0g of solid component obtained after grinding
was dispersed in 100 ml of a solvent mainly composed of isoparaffin having 10 to 11 carbon atoms (IP-1620 manufactured by Idemitsu Petroleum Science Co., Ltd.) to prepare a catalyst slurry.

Using the same polymerization apparatus as in Example 1, polymerization was carried out under the same conditions as in Example 1, except that 1.0 ml of the obtained catalyst slurry and 0.14 mmol of triethylaluminum were used as the catalyst component (B). I did it. The results are in Table 1
It was shown to. The short chain branching degree distribution is from the elution temperature of 50°C to 10°C.
A sharp pattern with a sharp peak near 90°C was observed in the 0°C range.

4,

[Brief explanation of drawings]

Figure 1 shows Catalyst preparation diagram in the present invention (flow chart) shows.

Claims (1)

[Claims] (1) When polymerizing ethylene or copolymerizing ethylene with at least one α-olefin in the presence of a catalyst consisting of a transition metal compound and an organometallic compound at a reaction temperature equal to or higher than the melting point of the polymer, component (A) is used. As a result, a solid component obtained by co-pulverizing (I) magnesium dihalide and (II) titanium trihalide is further treated in a suspended state with a solid catalyst component obtained by treating with (III) a titanium halide compound. , As the (B) component, (a) an organoaluminum compound represented by the general formula AIR^1_3 (in the formula, R^1 represents an alkyl group having 1 to 20 carbon atoms), (b) a general formula AlR^ 2_3X^1_3_-_1 (in the formula, R^2 represents an alkyl group having 1 to 20 carbon atoms, X^1 represents a halogen atom, and j is 0<j≦2
(c) an organoaluminum compound represented by the general formula AlR^3_k(OR^4)_3_-_k
(In the formula, R^3 and R^4 represent an alkyl group having 1 to 20 carbon atoms, and k represents a number of 1≦k≦2.) Or an aluminoxane, A method for producing polyethylene, the method comprising using a catalyst system comprising a mixture of at least two of the group consisting of: