JPH1192520A - Catalyst for ethylene polymer and method for producing ethylene polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst for producing an ethylene polymer having a wide molecular weight distribution suitable for film molding or blow molding, and a method for producing an ethylene polymer. A solid component comprising a reaction product of a chromium halide compound (a-1), a cyclic silazane compound (a-2) and a silylamide salt (a-3) supported on an inorganic oxide solid (a-4). A)
For an ethylene-based polymer obtained by reacting the above with alumoxane (B), a method for producing an ethylene-based polymer using the catalyst, and an ethylene-based polymer having a wide molecular weight distribution obtained by the method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a catalyst for producing an ethylene polymer and a method for producing an ethylene polymer.
More specifically, a novel chromium-based catalyst effective for producing an ethylene polymer having a wide molecular weight distribution or a copolymer of ethylene and an α-olefin, a method for producing an ethylene-based polymer using the catalyst, And an ethylene polymer obtained by the method.

[0002]

2. Description of the Related Art Ethylene homopolymers and copolymers of ethylene and α-olefin containing ethylene as a main component (hereinafter, both are collectively referred to as ethylene copolymer).
Is generally and widely used as a resin material for various molded articles. Ethylene polymers differ in required properties depending on the molding method and application. For example, a polymer having a relatively low molecular weight and a narrow molecular weight distribution is suitable for a product molded by an injection molding method, whereas a product having a relatively high molecular weight is suitable for a product molded by a film molding or blow molding. Polymers having a wide molecular weight distribution are suitable.

[0003] The molecular weight distribution is related to the surface skin of a film or blown product, and it is considered that the wider the molecular weight distribution, the less the surface roughness of the molded product. That is, even in the case of a polymer having a high molecular weight, it is possible to obtain a high quality product having good fluidity without causing melt fracture on the surface skin of the molded product.

Heretofore, ethylene polymers having a wide molecular weight distribution have chromium trioxide or any chromium compound which can be oxidized to chromium trioxide under the employed activation conditions supported on an inorganic oxide solid such as silica. It is known that they can be obtained by using a so-called Phillips catalyst.

In addition, Japanese Patent Publication No. 44-2996, Japanese Patent Publication No. 44-3827
And JP-B-47-1766, an ethylene polymer having a wide molecular weight distribution can be obtained by using a catalyst in which chromate esters are supported on an inorganic oxide solid such as silica.

Also, US Pat. No. 5,104,841 and US Pat.
As described in US Pat. No. 37,997, an ethylene polymer having a wide molecular weight distribution has been obtained by using a catalyst in which a reaction product of chromium dichloride and lithium bis (trimethylsilyl) amide is supported on an inorganic oxide solid.

Further, as described in Japanese Patent Publication No. 7-503739, an ethylene polymer having a wide molecular weight distribution can be obtained by a catalyst system in which chromium acetylacetonate is supported on silica and a catalyst system using alumoxane. ing. However, the ethylene-based polymer obtained with these catalysts has a number average molecular weight (Mw) based on the weight average molecular weight (Mw).
n) a molecular weight distribution (Mw / Mn) represented by the ratio of 5
It is about 70, and an ethylene polymer having a wider molecular weight distribution may be required depending on the use.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides an ethylene-based polymer having a wider molecular weight distribution, particularly a molecular weight distribution (M
(w / Mn) is a catalyst for an ethylene polymer capable of reliably and stably producing an ethylene polymer having an extremely wide range of 80 to 150, and an ethylene polymer having a wide molecular weight distribution (Mw / Mn) using the catalyst. Production method and molecular weight distribution (M
(w / Mn) is 80-150.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above problems and found that 1) a chromium halide compound (a-1), a cyclic silazane compound (a-2) and a silylamide salt (a (3) a catalyst for an ethylene-based polymer obtained by reacting a solid component (A) in which the reaction product of (3) is supported on an inorganic oxide solid (a-4) with alumoxane (B); 1 mol of the chromium halide compound (a-1) is reacted at a molar ratio of 0.5 to 1.5 mol of the cyclic silazane compound (a-2) and 1 to 3 mol of the silylamide salt (a-3). The product is made into a solid component by supporting 0.01 to 10% by weight of chromium atoms with respect to the inorganic oxide solid (a-4).
2. The ethylene-based polymerization catalyst according to the above 1, wherein the solid component (A) is reacted with alumoxane (B) such that the ratio of aluminum atoms / chromium atoms becomes 1 to 1000.

3) The solid component (A) is prepared by mixing alumoxane (B) with aluminum / chromium at a ratio of 5 to 30.
The catalyst for ethylene-based polymerization according to the above item 2, wherein the catalyst is reacted so as to have a ratio of 0; 4) a method for producing an ethylene-based polymer, characterized by using the catalyst according to any of the above items 1 to 3, 5) The molecular weight distribution (Mw /
The above object has been achieved by developing an ethylene polymer having an Mn of 80 to 150.

Hereinafter, the present invention will be described specifically. As the chromium halide compound (a-1) used for preparing the catalyst for ethylene polymerization of the present invention, a chromium trihalide compound is preferable, and specific examples thereof include chromium trichloride, chromium trifluoride, chromium tribromide, and chromium tribromide. Examples thereof include halides such as chromium iodide, and among them, chromium trichloride or chromium tribromide is preferable. Further, a tetrahydrofuran complex of chromium trichloride (CrCl ₃ .3THF) is also preferably used.

The cyclic silazane compound (a-2) includes a compound represented by the following general formula (1).

Embedded image In the above formula, R ¹ , R ² and R ³ represent hydrogen or carbon atom 1
Represents an alkyl group having 10 to 10 or an aromatic group having 6 to 20 carbon atoms, and n is an integer of 4 to 18.

Specifically, 1,1,3,3-tetramethylcyclodisilazane, 1,2,3,4-tetramethylcyclodisilazane, 1,1,2,3,3,4-hexamethyl Disilazane, 1,1,3,3,5,5-hexamethylcyclotrisilazane, 1,2,3,4,5,6-hexamethylcyclotrisilazane, 1,1,2,3,3,4 ,
5,5,6-nonamethylcyclotrisilazane, 1,1,
3,3,5,5,7,7-octamethylcyclotetrasilazane, 1,2,3,4,5,6,7,8-octamethylcyclotetrasilazane, 1,1,2,3,3,3 4,
5,5,6,7,7,8-octamethylcyclotetrasilazane and the like, particularly 1,1,3,3,5,5-
Hexamethylcyclotrisilazane, 1,2,3,4
5,6-hexamethylcyclotrisilazane, 1,1,
2,3,3,4,5,5,6-nonamethylcyclotrisilazane is preferably used.

As the silylamide salt (a-3), a silylamide salt obtained by reacting a primary and / or secondary silylamine with an alkali metal and / or an alkaline earth metal is used. As a specific example, a bis (trialkylsilyl) amide salt such as lithium bis (trimethylsilyl) amide, sodium bis (trimethylsilyl) amide, lithium bis (triethylsilyl) amide, and sodium bis (triethylsilyl) amide is preferable.

The reaction between the chromium halide compound (a-1), the cyclic silazane compound (a-2) and the silylamide salt (a-3)
Diethyl ether, tetrahydrofuran, dioxane,
The reaction is performed in an ether solvent such as 1,2-dimethoxyethane. As a solvent for the reaction, tetrahydrofuran or 1,2-dimethoxyethane is particularly preferred.
The reaction between the chromium halide compound and the cyclic silazane compound or the silylamide salt is preferably performed at a molar ratio of 0.5 to 1.5 mols of the cyclic silazane compound and 1 mol of the silylamide salt to 1 mol of the chromium halide. .

The order of the reaction is such that a chromium halide compound is reacted with a cyclic silazane compound and then a silylamide salt, or a chromium halide compound is reacted with a silylamide salt and then a cyclic silazane compound is reacted. The order of the reaction may be any method. The reaction temperature at this time is -78 ° C to the boiling point of the solvent, preferably -20 ° C to 60 ° C, and the reaction time is 10 minutes to 48 hours, preferably 30 minutes to 24 hours. As a result of this reaction, for example, in the case of a reaction of chromium trichloride, 1,1,3,3,5,5-hexamethylcyclotrisilazane and lithium bis (trimethylsilyl) amide, lithium chloride precipitates. Preferably, the precipitated salts are removed. After filtration, the ether solvent is removed under reduced pressure, and the resultant is dissolved in an inert hydrocarbon solvent such as pentane, hexane, heptane, cyclohexane, benzene, toluene, xylene, etc. to obtain a reaction product.

The inorganic oxide solid (a-4) is an oxide of a metal belonging to Group 2, 4, 13, or 14 of the periodic table, and specifically, magnesia, titania, zirconia, silica, alumina, Silica-alumina, silica-titania,
Examples thereof include silica-zirconia, aluminum phosphate, and mixtures thereof. Preferred among these are silica-alumina and silica.

The inorganic oxide solid (a-4) has a specific surface area of 50 to 1000 m ² / g, preferably 20 to 1000 m ² / g.
0-800 m ² / g, pore volume 0.5-3.0 m ² / g, preferably 1.0-2.5 m ² / g, average particle size 10-200 μm
m, preferably in the range of 50 to 150 μm. It is desirable that the inorganic oxide solid (a-4) be baked before use by removing adsorbed moisture. The calcination of the inorganic oxide solid is usually performed under a molecular sieve flow in a dry nitrogen gas stream at 100 to 900
C., preferably in the temperature range of 400 to 800 C. (500 C. in the example) for 30 minutes to 24 hours. It is preferable to supply a sufficient amount of nitrogen gas to dry the inorganic oxide solid in a fluid state.

The reaction product of the chromium halide compound (a-1), the cyclic silazane compound (a-2) and the silylamide salt (a-3) is supported on the inorganic oxide solid (a-4) by using pentane, It is carried out in an inert hydrocarbon solvent such as hexane, heptane, cyclohexane, benzene, toluene, xylene and the like. The amount of the reaction product supported on the inorganic oxide solid (a-4) is added so that the supported amount of chromium atoms is 0.01 to 10 wt%, preferably 0.05 to 5 wt%. The reaction temperature is -78 ° C to the boiling point of the solvent, preferably -20 ° C to 50 ° C.
C., and the reaction time is 10 minutes to 24 hours, preferably 30 minutes.
Minutes to 5 hours. After the supporting reaction, the solid component (A) having good fluidity can be obtained by a method of removing the solvent under reduced pressure or a method of separating by filtration.

The inorganic oxide solid component (A) supporting the reaction product of the chromium halide compound (a-1), cyclic silazane compound (a-2) and silylamide salt (a-3) is converted to alumoxane (B) The catalyst for producing an ethylene-based polymer of the present invention is obtained by reacting

Alumoxane (B) is a compound well known in the art. Its manufacturing method and structure are Poly
hedron, 9 , 429-453 (1990); Ziegler Catalysts, G.
This is described in detail in Fink et al. (Eds.) 57-82, Springer-Verlag (1995) and the like. The alumoxane used in the present invention includes a compound represented by the following general formula (2) or (3).

[0022]

Embedded image

In the above formula, R ⁴ is a methyl group, an ethyl group,
It is a hydrocarbon group such as a propyl group, an n-butyl group and an isobutyl group, and is preferably a methyl group and an isobutyl group. Processes for producing compounds of this type are known, and for example, inert carbonized salts such as pentane, hexane, heptane, cyclohexane, decane, benzene and toluene having salts of water of crystallization (such as copper sulfate hydrate and aluminum sulfate hydrate). There are a method in which a trialkylaluminum is added to a suspension of a hydrogen solvent and a method in which solid, liquid or gaseous water is allowed to act on the trialkylaluminum in a hydrocarbon solvent.

Further, an alumoxane represented by the following general formula (4) or (5) may be used.

Embedded image

In the above formula, R ⁵ is a methyl group, an ethyl group,
It is a hydrocarbon group such as a propyl group, an n-butyl group and an isobutyl group, and is preferably a methyl group and an isobutyl group. R ⁶ represents a methyl group, an ethyl group, a propyl group, n
- butyl group, a hydrocarbon group such as an isobutyl group or a chlorine, a halogen such as bromine or hydrogen, is selected from hydroxyl, they exhibit different radicals from R ^5. A plurality of R ⁵ and R ⁶ in the molecule may be the same or different. q is usually an integer of 1 to 100, preferably 3 or more;
q + r is 2 to 100, preferably 6 or more.

In the general formula (4) or (5), the following units

Embedded image May be connected in blocks or may be connected regularly or irregularly at random. Such an alumoxane is obtained by using two or more kinds of trialkylaluminums instead of one kind of trialkylaluminum in the same manner as the above-mentioned alumoxane of the general formula,
It can be produced using one or more kinds of trialkylaluminum and one or more kinds of dialkylaluminum monohalide or dialkylaluminum monohydride.

The above solid component (A) is converted to alumoxane (B)
The reaction is carried out in an inert hydrocarbon such as pentane, hexane, heptane, cyclohexane, benzene, toluene, xylene and the like. Solid component (A)
The reaction is preferably carried out in such an amount that the aluminum atom in the alumoxane (B) used for the reaction becomes an aluminum atom / chromium atom ratio of 1 to 1000, preferably 5 to 300 with respect to the chromium atom therein. Reaction temperature is -78
C to the boiling point of the solvent, preferably -20C to 60C, and the reaction time is 10 minutes to 24 hours, preferably 30 minutes to 5 hours. After the reaction, a catalyst having good fluidity can be obtained by a method of removing the solvent under reduced pressure or a method of separating by filtration.

In carrying out the polymerization of the ethylene polymer of the present invention, the polymerization method may be a liquid phase polymerization method such as slurry polymerization or solution polymerization, or a gas phase polymerization method. The liquid phase polymerization method is usually carried out in a hydrocarbon solvent, and as the hydrocarbon solvent, an inert hydrocarbon such as butane, isobutane, hexane, cyclohexane, benzene, toluene, xylene or a mixture thereof is used.
The polymerization temperature is generally 0 to 300 ° C., and practically 2
0-200 ° C. The catalyst concentration and ethylene pressure in the reactor may be any concentration and pressure as long as they are sufficient for the polymerization to proceed. Further, hydrogen or the like can coexist in the polymerization system for controlling the molecular weight. Further, if necessary, together with ethylene, an ethylene copolymer is obtained by using α-olefin such as propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene alone or two or more kinds. be able to. By performing the method of the present invention, the number average molecular weight (Mn) is 2,000
0-20,000, weight average molecular weight (Mw) 200,000-600,00
At 0, an ethylene polymer having a Mw / Mn of 80 to 150 and a wide molecular weight distribution can be obtained.

[0029]

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In Examples and Comparative Examples, the molecular weight and molecular weight distribution of the produced ethylene polymer were measured by gel permeation chromatography (GPC). That is, the number average molecular weight (Mn) and the weight average molecular weight (M
w) was determined, and the molecular weight distribution was determined as the ratio of Mw to Mn (Mw / Mn). Mw / Mn indicates that the larger the value, the wider the molecular weight distribution. The conditions for gel permeation chromatography (GPC) measurement are as follows. Apparatus: WATERS 150C model, Column: Shodex-HT806M, Solvent: 1,2,4-trichlorobenzene, Temperature: 135 ° C, Sample concentration: 2mg / 5ml, Universal rating using monodisperse polystyrene fraction.

[0030] Example 1 (1) CrCl ₃ and 1,1,3,3,5,5 hexamethylcyclotrisilazane reaction CrCl ₃ · 3THF complex (Aldrich Co.) 2.40 g (6.41
(mmol) was dissolved in 150 ml of tetrahydrofuran. 3.50 ml of 1,1,3,3,5,5-hexamethylcyclotrisilazane (Shin-Etsu Chemical) at room temperature (14.64 mm
ol) and stirred for 90 minutes. The solvent was removed under reduced pressure to obtain a green mass. When 70 ml of hexane was added thereto, a green powdery precipitate was obtained. The liquid part was drawn out by decantation, 70 ml of hexane was further added, and the liquid part was drawn out again by decantation. The solvent was removed under reduced pressure to obtain 2.0 g of a grayish green powdery solid. When the chromium content in the reaction product was measured by atomic absorption method, the chromium content was 17.0
3%.

(2) CrCl ₃ and 1,1,3,3,5
Reaction of the reaction product of 5-hexamethylcyclotrisilazane with lithium bis (trimethylsilyl) amide To 1.55 g (5.08 mmol in terms of chromium atom) of the reaction product obtained in the above (1), 150 ml of tetrahydrofuran was added and dissolved. . At room temperature, 15.2 ml (15.2 mmol) of a 1.0 mol / liter-lithium bis (trimethylsilyl) amide (manufactured by Aldrich) hexane solution was added, and the mixture was heated and refluxed for 1 hour. After removing by-product lithium chloride by filtration with a glass filter, the solvent was removed under reduced pressure,
100 ml of toluene was added and dissolved. When the chromium concentration of the obtained reaction solution was measured, it was 0.00494 mmol-
Cr / ml (0.257 mg-Cr / ml).

(3) Preparation of catalyst 952 grade silica (average particle size: 80 μm, specific surface area: 300 m ² / g, pore volume: 1.6 cm ³ / g) manufactured by DAVISON, which was calcined at 300 ° C. for 8 hours. 30 ml of hexane was added to g to form a slurry. 13.5 ml (3 mg in terms of chromium atom) of the reaction solution obtained in (2) was added, and the mixture was stirred at 40 ° C. for 1 hour. Further, 6.7 ml (8.0 mmol) of a 1.2 mol / liter-hexane solution of isobutylalumoxane manufactured by Tosoh Akzo was added, and the mixture was stirred at 40 ° C. for 1 hour. The solvent was removed under reduced pressure to obtain a catalyst.

(4) Polymerization In a 1.5 liter autoclave sufficiently purged with nitrogen, 0.6 liter of isobutane and 0.12 of the catalyst obtained in (3) were added.
g, and the internal temperature was raised to 100 ° C. Then, ethylene was injected under pressure, and polymerization was carried out for 1 hour while maintaining the ethylene partial pressure at 14 kg / cm ² . Then, the polymerization was terminated by discharging the content gas out of the system. As a result, 36 g of polyethylene was obtained. The polymerization activity per 1 hour of catalyst per 1 hour of polymerization time was 300 g / g ·
hr. As a result of GPC measurement, Mn = 2400, Mw =
310000, Mw / Mn = 129.

Example 2 In Example 1 (3), 2.7 m of methylalumoxane manufactured by Tosoh Akzo was used instead of isobutylalumoxane.
ol / liter-toluene solution 3.0 ml (8.1 mmol)
l) A catalyst was prepared and polymerized in the same manner as in Example 1 except that it was added. As a result, 40 g of polyethylene was obtained. The polymerization activity per gram of catalyst and per hour of polymerization time was 333 g / g · hr. As a result of GPC measurement, Mn = 2600, Mw = 360,000, Mw / Mn = 138
Met.

Example 3 A catalyst was prepared and polymerized in the same manner as in Example 1 except that the amount of isobutylalumoxane added was 3.3 ml (4.0 mol). as a result,
34 g of polyethylene were obtained. The polymerization activity per 1 hour of the polymerization time per 1 g of the catalyst was 283 g / g · hr. As a result of GPC measurement, Mn = 2400, Mw = 31000
0, Mw / Mn = 129.

Example 4 In Example 1 (3), the added amount of the reaction product solution obtained in Example 1 (2) was 23.3 ml (6 m in terms of chromium atom).
A catalyst was prepared and polymerized in the same manner as in Example 1 except that g) was used. As a result, 52 g of polyethylene was obtained. The polymerization activity per 1 g of the catalyst and per hour of the polymerization time was 433 g / g · hr. As a result of GPC measurement, Mn was 2100, Mw was 260,000, and Mw / Mn was 124.

Example 5 Polymerization was carried out in the same manner as in Example 1 except that hydrogen was introduced at 5 kg / cm ² and the polymerization temperature was changed to 95 ° C. As a result, 27 g of polyethylene was obtained. The polymerization activity per 1 g of the catalyst and per one hour of the polymerization time was 225 g / g · hr. As a result of GPC measurement, Mn = 2100, Mw = 260,000, Mw / Mn = 124.
Met.

Example 6 Polymerization was carried out in the same manner as in Example 1 except that 20 ml of 1-hexene was introduced. As a result, 39 g of polyethylene was obtained. The polymerization activity per one hour of the catalyst per one hour of the polymerization time is 325 g / g.
Hr. As a result of GPC measurement, Mn = 2200, Mw
= 260,000 and Mw / Mn = 118.

COMPARATIVE EXAMPLE 1 As a so-called Phillips catalyst in which chromium trioxide is supported on silica, EP30X catalyst (chromium carrying amount: 1.0 wt%) manufactured by Crossfield Co., Ltd. was heated at 820 ° C. in air.
Using a catalyst calcined for 18 hours, polymerization was carried out under the same conditions as in Example 1 (4). As a result, 210 g of polyethylene was obtained. The polymerization activity per 1 g of the catalyst per 1 hour of the polymerization time was 1,750 g / g · hr. As a result of GPC measurement, Mn = 13000, Mw = 120,000, Mw / Mn =
9.2, and the molecular weight distribution was narrower than in Examples 1 to 6.

Comparative Example 2 In Example 1 (3), 0.12 g of a solid component and 1.0% of a solid component obtained without treatment with isobutylalumoxane were used.
Polymerization was carried out in the same manner as in Example 1 except that 0.5 ml of a hexane solution of mol / liter-triisobutylaluminum was charged. As a result, 6 g of polyethylene was obtained. The polymerization activity per 1 hour of the polymerization time per 1 g of the catalyst was 50 g / g · hr. As a result of the GPC measurement,
Mn = 9200, Mw = 380,000, Mw / Mn = 41,
The molecular weight distribution was narrower than in Examples 1-6.

The results of the above Examples and Comparative Examples are shown in a table.

[Table 1]

[0042]

According to the present invention, a high-quality ethylene polymer having a wide molecular weight distribution and suitable for film molding and blow molding can be produced efficiently and industrially advantageously.

[Brief description of the drawings]

FIG. 1 is a flowchart of catalyst preparation in the method for producing an ethylene polymer of the present invention.

Claims (5)

[Claims] 1. A solid component in which a reaction product of a chromium halide compound (a-1), a cyclic silazane compound (a-2) and a silylamide salt (a-3) is supported on an inorganic oxide solid (a-4). (A)
With an alumoxane (B) to obtain an ethylene polymer catalyst. 2. A mole ratio of the cyclic silazane compound (a-2) and the silylamide salt (a-3) in a mole ratio of 0.5 to 1.5 moles and a silylamide salt (a-3) in a mole ratio of 1 mole to 1 mole of the chromium halide compound (a-1). And reacting the reaction product with the inorganic oxide solid (a-4).
A solid component (A) is prepared by supporting 0.01 to 10 wt% as chromium atoms, and the solid component (A) is converted to alumoxane (B)
The ethylene-based polymerization catalyst according to claim 1, which is obtained by reacting so that a ratio of aluminum atom and chromium atom becomes 1 to 1000. 3. The catalyst for ethylene polymerization according to claim 2, which is obtained by reacting the solid component (A) with the alumoxane (B) such that the ratio of aluminum atom / chromium atom is 5 to 300. 4. A method for producing an ethylene-based polymer, comprising using the catalyst according to any one of claims 1 to 3. 5. An ethylene polymer having a molecular weight distribution (Mw / Mn) of from 80 to 150 obtained by the method of claim 4.