JPH0414122B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing polyolefin. More specifically, it is a two-stage polymerization process using specific catalysts and cocatalysts under specific conditions to achieve excellent rigidity, environmental cracking resistance, and moldability (i.e., extrudability and balance effect), and to prevent buildup. This invention relates to a method for producing a polymer that is difficult to process. [Prior art] In general, in blow molding and extrusion molding of polyolefins, extrudability and balance effect are important in the molding process, and in terms of physical properties, it is important that the material has excellent environmental cracking resistance, impact strength, etc., and is free from fiber eyes. Therefore, high rigidity is sometimes desired for some blow molding. In the case of so-called high-density polyethylene, the higher the average molecular weight, the better the physical properties such as impact resistance and environmental cracking resistance. On the other hand, high-density polyethylene is generally commercialized by melt molding, but when the average molecular weight is increased to provide the above-mentioned characteristics, flow during melting is poor, causing melt fracture and rough skin, and moldability is reduced. Therefore, there is a method of widening the molecular weight distribution in order to have both. When the molecular weight distribution is widened, the flow rate ratio (FR), which will be defined later, increases, the extrudability improves, and therefore the molding speed can be increased. However, as the flow rate ratio increases, the balance effect generally increases, which has the disadvantage that the balisong becomes thicker and thicker during blow molding, and when extruded sheet molding.
It has the disadvantage that edge tear occurs. In addition, to increase the rigidity, the density may be increased, but the environmental cracking resistance generally deteriorates. As a method for obtaining high-density polyethylene with environmental crack resistance and formability,
No. 5208 and No. 45-3215 propose compositions in which high molecular weight polyethylene is blended with low molecular weight polyethylene. Methods for mixing these compositions include blending using a batch-operated Banbury mixer or blending a solution of polyolefin dissolved in a solvent, but both methods have low productivity in commercial production and tend to cause fish eyes. [Means for Solving the Problems] Therefore, the present inventors have conducted extensive studies on a method for producing polyolefin that has excellent extrudability, has a low balance effect, has excellent environmental cracking resistance, and is less likely to cause hard eyes. Polymer blend ratio, molecular weight,
In addition to specifying the degree of copolymerization, by specifying the catalyst for polyethylene production, it is possible to obtain polyethylene that has excellent rigidity, environmental cracking resistance, and moldability (extrudability and balance effect), and is resistant to the formation of hard eyes. A polymerization method was discovered and the present invention was achieved. That is, the gist of the present invention is to homopolymerize ethylene or copolymerize ethylene with other α-olefins at a temperature of 50 to 100°C in a hydrocarbon solvent using a catalyst system consisting of a transition metal compound component and an organoaluminum compound. When performing this, a solid catalyst component which is a reaction product of an oxygen-containing organic compound of magnesium, an oxygen-containing organic compound of titanium, and an aluminum halide compound is used as a transition metal compound component,
An alkylaluminum sesquichloride is used as the organoaluminum compound, and (a) the polymerization reaction is carried out in two stages, that is, in the presence of the reaction mixture obtained by polymerization in the first reaction zone, the second
(b) In one of the first and second reaction zones, polymerization is carried out in the presence of hydrogen in a molar ratio of 0.001 to 1.5 to ethylene in the gas phase. Polymer A with a viscosity average molecular weight of 150,000 to 1,000,000 was produced in an amount of 10% to 70% by weight of the total polymer production, and in the other zone, the molar ratio to ethylene in the gas phase was
Polymer B with a viscosity average molecular weight of 10,000 to 80,000 was polymerized in the presence of 1.5 to 15 hydrogen, and 90 of the total polymer production amount was obtained.
% to 30% by weight, and further (polymer A
(viscosity average molecular weight of polymer B)/(viscosity average molecular weight of polymer B) is 4 to 80, and (c) the melt index of all the polymers finally produced is less than 0.5 g/10 minutes. It consists in a method for producing polyolefin. To explain the present invention in more detail, the catalyst system used in the present invention is a solid catalyst component which is a reaction product of an oxygen-containing organic compound of magnesium, an oxygen-containing organic compound of titanium, and an aluminum halide compound as a transition metal compound component. This is a catalyst system consisting of an alkyl aluminum sesquichloride as an organoaluminum compound used as a cocatalyst. By using this catalyst system and producing polyolefin under the production conditions described below,
A polymer with excellent rigidity, environmental cracking resistance, and moldability (that is, extrudability and balance effect), and which is less likely to cause hard eyes, can be obtained. This is an advantage over polyolefins made using catalyst systems such as dialkyl aluminum chlorides. The oxygen-containing organic compound of magnesium used in preparing the solid catalyst component used in the present invention is Mg(OR ¹ ) _n X ¹ _2-n (wherein R ¹ is an alkyl group,
aryl group or cycloalkyl group, X ¹ represents a halogen atom, m represents 1 or 2), such as magnesium diethoxide, magnesium dimethoxide, magnesium diphenoxide, magnesium monoethoxy chloride, Examples include magnesium monophenoxy chloride, magnesium monoethoxy bromide, magnesium monoethoxy iodide, and the like. Among these, magnesium ethoxide is preferred. As an oxygen-containing organic compound of titanium, the general formula is
Ti(OR ² ) _o X ² _4-o (wherein, X ² represents a halogen atom,
R ² represents an alkyl group, an aryl group, or a cycloalkyl group, and n represents a number from 1 to 4), such as tetraethoxytitanium, tetra-n-butoxytitanium, diethoxydichlorotitanium, di- n-butoxydichlorotitanium, triethoxymonochlortitanium, tri-n-butoxymonochlortitanium, ethoxytrichlortitanium, n-
Examples include butoxytrichlortitanium, methoxytribromotitanium, and the like. Among these, tri-n-butoxymonochlorotitanium is preferred. As an aluminum halide compound, the general formula is
_Compounds represented by ^{AlR 3 p} Examples include aluminum dichloride, ethylaluminum sesquichloride, diethylaluminum monochloride, normal propylaluminum dichloride, and the like. Among these, ethylaluminum sesquichloride is preferred. In the reaction of the above compounds, first, an oxygen-containing organic compound of magnesium and an oxygen-containing organic compound of titanium are mixed and heated to 100°C to 160°C to prepare a uniform liquid. When it is difficult to produce a uniform liquid, it is preferable to include alcohol. Examples of the alcohol include ethyl alcohol, n-butyl alcohol, and n-octyl alcohol. An inert hydrocarbon solvent is then added to form an inert hydrocarbon solution. An aluminum halogen compound is added to the inert hydrocarbon solution obtained as described above, and the mixture is heated to room temperature.
When the reaction is carried out at 100°C, the reaction product is obtained as a precipitate, and unreacted substances are washed away with an inert hydrocarbon solvent. The quantitative ratio of each component is the molar ratio of titanium compound to magnesium compound (Ti/Mg) of 0.1 to 10, and the ratio of the number of moles of aluminum halogen compound to the sum of the number of moles of magnesium compound and the number of moles of titanium compound [Al compound ]/[Mg compound]+[Ti compound] is preferably 1 to 20. The most distinctive feature of the present invention is the use of alkylaluminium sesquichloride as a cocatalyst to be combined with the solid catalyst component,
As a result, by producing a polyolefin under the production conditions described below, a polymer that is less likely to cause fish eyes in the produced polymer and has excellent moldability (extrudability and balance effect) and environmental cracking resistance can be obtained. Specifically, the alkylaluminum sesquichloride includes ethylaluminum sesquichloride, isobutylaluminum sesquichloride,
Examples include isopropyl aluminum sesquichloride. Preferably, ethylaluminum sesquichloride is used. In the present invention, the above catalyst system is used to carry out homopolymerization of ethylene or copolymerization of ethylene with other α-olefins at a temperature of 50° C. to 100° C. in a hydrocarbon solvent. Hydrocarbon solvents include hexane,
Inert hydrocarbon solvents include aliphatic hydrocarbons such as heptane, aromatic hydrocarbons such as benzene, toluene, and xylene, and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane. Other α-olefins that are copolymerization components have the general formula R ⁴ −CH=CH ₂ (wherein R ⁴ has a carbon number of 1
~12 alkyl groups),
For example, propylene, butene-1, hexene-1,
Examples include 4-methylpentene-1 and octene-1. The content of the copolymer component is usually 5 mol% or less in the polymer. Therefore, in the present invention, the polymerization reaction is carried out under the following conditions (a), (b), and (c). (a) The polymerization reaction is carried out in two stages, that is, the reaction mixture obtained by polymerization in the first reaction zone is further polymerized in the second reaction zone. (b) In either the first or second reaction zone, a polymer having a viscosity average molecular weight of 150,000 to 1,000,000 is produced by polymerizing in the presence of hydrogen at a molar ratio of 0.001 to 1.5 to ethylene in the gas phase. A is produced in an amount of 10% to 70% by weight of the total polymer production amount, and in the other zone is polymerized in the presence of hydrogen in a molar ratio of 1.5 to 15 to ethylene in the gas phase to obtain a viscosity average molecular weight of 10,000 to 10,000. 80,000 Polymer B is produced in an amount of 90% to 30% by weight of the total amount of produced polymer, and further, (viscosity average molecular weight of Polymer A)/(viscosity average molecular weight of Polymer B) is set to 4 to 80. . (c) The melt index of all the polymers finally produced is less than 0.5. To explain these three conditions (a), (b), and (c), the two-step polymerization in (a) can be carried out in either a continuous polymerization method or a batch polymerization method. In the case of continuous polymerization, two reactors are connected in series, and the reaction mixture obtained by polymerization in the first reactor is transferred to the second reactor.
into the reactor to continue polymerization. If necessary, a flash tank capable of purging most of the hydrogen is installed between the two reactors. In the case of batch polymerization, the reactions are carried out sequentially in one reactor. Among these, continuous polymerization is preferred. According to the reaction conditions (b), first, the first and second
Polymerization is carried out in one of the reaction zones in the presence of hydrogen in a molar ratio of 0.001 to 1.5 to ethylene in the gas phase, and 10% to 70% by weight of the total amount of the final polymer produced. % by weight of Polymer A is produced, and the viscosity average molecular weight of the Polymer A obtained here is 150,000 to 1,000,000. The viscosity average molecular weight is
^The intrinsic viscosity in a tetralin solution at 130°C was measured, and [η] = 4.60 × 10 ^-4 × M ^0.725 ([η] is the intrinsic viscosity,
M is a value calculated from the formula for viscosity average molecular weight.
When polymer A is produced in the second reaction zone in the presence of polymer B produced in the first reaction zone, the viscosity average molecular weight of polymer A is expressed by the following formula: [η] _A = (100 [η] - _{W B} [η] _B ) / W _A (where, [η] _A indicates the intrinsic viscosity of polymer A,
[η] _B indicates the intrinsic viscosity of polymer B, [η] is the second
indicates the intrinsic viscosity of the total polymer finally obtained in the reaction zone, W _A indicates the weight percent of polymer A produced in the second reaction zone, and W _B indicates the weight percent of polymer A produced in the first reaction zone. The viscosity average molecular weight can be calculated by finding [η] _A from (indicates the weight percent of the combined B). However, if the viscosity average molecular weight is less than 150,000, the impact strength, tear strength, and environmental cracking resistance of the resulting polymer (the total polymer finally produced) will be low, and if it exceeds 1,000,000, the moldability will decrease. becomes low, which is not desirable. The preferred range is 230,000 to 900,000, particularly preferably 300,000 to 800,000. When the molar ratio of hydrogen to ethylene in the gas phase is less than 0.001, the viscosity average molecular weight often exceeds 1 million, and when it exceeds 1.5, the viscosity average molecular weight often becomes less than 100,000, which is not preferable. If the amount produced is less than 10% by weight, the impact strength and environmental cracking resistance of the resulting polymer (finally produced polymer) will be low, and the balance effect will become large, and if it exceeds 70% by weight, the moldability will be poor. I don't like it. A preferred range is 15% to 50% by weight, especially 20% to 40% by weight. The polymerization reaction may be carried out at 50° C. to 100° C. for 10 minutes to 10 hours under a pressure of 0.5 Kg/cm ² gauge to 100 Kg/cm ² gauge. Polymer A is preferably a copolymer, and the content of the copolymer component is 0.5 mol%.
The content is preferably 4 mol%, preferably 0.5 mol% to 3 mol%, from the viewpoint of moldability or environmental cracking resistance. Next, in the other reaction zone, polymerization is carried out in the presence of hydrogen in a molar ratio of 1.5 to 15 to ethylene in the gas phase to finally produce a polymer B having a viscosity average molecular weight of 10,000 to 80,000. 90 of the total production of total polymers
% to 30% by weight. The viscosity average molecular weight is
Measure the intrinsic viscosity in a tetralin solution at 130℃,
It can be calculated from the formula shown above. When polymer B is produced in the second reaction zone in the presence of polymer A produced in the first reaction zone, the viscosity average molecular weight of polymer A is expressed by the following formula [η] _B = (100 [η]−W′ _A [η] _A )/W′ _B (wherein, [η] _B represents the intrinsic viscosity of polymer B,
[η] represents the intrinsic viscosity of the entire final polymer obtained in the second reaction zone, W′ _A represents the weight percent of polymer A obtained in the first reaction zone, and W′ _B represents the total intrinsic viscosity of the final polymer obtained in the second reaction zone.
(indicates the weight percent of polymer B obtained in the reaction zone)
Find [η] _B from and calculate the viscosity average molecular weight. However, if the viscosity average molecular weight is less than 10,000, the impact strength of the resulting polymer (the entire polymer finally produced) will decrease, and if it exceeds 80,000, the moldability will decrease, which is not preferable. When the molar ratio of hydrogen to ethylene in the gas phase is less than 1.5, the viscosity average molecular weight of polymer B often exceeds 80,000,
If it exceeds 15, it is often less than 10,000, which is not desirable. The preferred range is 20,000 to 60,000. If the amount produced exceeds 90% by weight, the impact strength and environmental cracking resistance of the resulting polymer (finally produced polymer) will decrease, the ballast effect will become large, and fish eyes will more likely occur, which is undesirable. If it is less than 30% by weight, moldability becomes low, which is not preferable.
A preferred range is 85% to 50% by weight, especially 80% to 60% by weight. The polymerization reaction may be carried out at 50° C. to 100° C. for 10 minutes to 10 hours under a pressure of 0.5 Kg/cm ² gauge to 100 Kg/cm ² gauge. Polymer B is preferably an ethylene homopolymer, but may also be a copolymer with a copolymer content of 2 mol% or less, preferably 1 mol% or less. From the viewpoint of rigidity, it is preferable that the content of the copolymer component is small. Regarding the order of polymerization, polymer A may be produced and then polymer B may be produced, or polymer B may be produced first and then polymer A may be produced. (Viscosity average molecular weight of polymer A)/(viscosity average molecular weight of polymer B) is 4 to 80, preferably 5 to 60. When this ratio is less than 4, moldability decreases,
If it exceeds 60, the balance effect will increase, which is not preferable. According to the condition (c), the melt index of the entire polymer finally produced, that is, the mixture of polymer A and polymer B, is set to be less than 0.5. Here, the melt index is a value measured at 190° C. under a load of 2.16 kg based on ASTM D-1238, and the unit is g/10 minutes. If it is 0.5 or more, the impact strength, environmental cracking resistance, etc. of the entire polymer finally produced will decrease, which is not preferable. Melt index 0.1~
At 0.5, the moldability and environmental cracking resistance are good, and the balance effect is particularly small, so advantages such as high-speed moldability and small edge tear can be obtained in blow molding and extrusion molding. When the melt index is 0.1 or less, the moldability is good, and when the melt index is less than 0.05, the moldability does not worsen, and surging of the extruder is less likely to occur, which is advantageous in the fields of thin-walled films, large-scale blowing, etc. It is preferable that the polymer produced as described above is then kneaded. The polymer obtained by the present invention is easily homogenized, and is homogenized and pelletized using a continuous kneading extruder. The polymer obtained after kneading has the advantage of having no stickiness. [Examples] Next, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Note that FIG. 1 is a flowchart diagram for understanding the technical content included in the present invention, and the present invention is not limited to this flowchart diagram. In addition, in the following examples, physical property tests were performed using the obtained polymer powder using a Gourmage screw extruder (40 rpm, temperature C ₁ = 160°C, 30 mmφ, L/D = 27,
Measurements were made using samples that were kneaded at C ₂ = 180°C, D = 190°C) and pelletized. The extrusion molding amount as a measure of moldability (extrudability) was measured using a Brabender Model 21D single screw extruder (bore 19.1
mmφ, L/D=21, compression ratio=3 full flight screw, die diameter 20mmφ, clearance 0.5
mm circular die), the die temperature is 200℃ and the rotation speed
The extrusion amount was measured at 150 revolutions/min, and the extrusion amount per revolution number was determined by dividing the extrusion amount by the number of revolutions (150 revolutions/min). The fixity was visually determined from this cylindrical melt extrudate. Environmental cracking resistance (abbreviated as ESCR) was measured by the bell telephone method described in ASTM D-1693. The time required for 5 out of 10 test pieces to break was expressed. Tensile impact strength was determined according to ASTM D-1822L. Melt index (abbreviated as MI) is ASTM
Measured based on D-1238 at 190°C and under a load of 2.16 kg. Flow rate ratio (abbreviated as FR) is ASTM D-1238
In a melt index device based on the above, the shear stress value was determined by the flow rate ratio (MI10 ⁶ /MI10 ⁵ ) at 10 ⁶ dyne/cm ² and 10 ⁵ dyne/cm ² . The α-olefin content was measured by infrared absorption spectroscopy, and the density was measured by JIS K6760 density gradient tube method. The ballast effect was measured using a Shimadzu flow tester with a diameter of 1 mm, L/D = 2, and an inflow angle to the nozzle.
It was expressed as (cross-sectional area of extruded material/cross-sectional area of nozzle) 1000 sec ^-1 at a temperature of 190°C using a 30° nozzle and a shear rate of 1000 sec ^-1 (abbreviated as α1000).
The smaller α1000, the smaller the balance effect. Examples 1 to 5, Comparative Examples 1 to 3 (1) Catalyst preparation 115 g of magnesium ethoxide, 151 g of tri-n-butoxymonochlorotitanium, and n-butanol
37g and were mixed at 140°C for 6 hours to homogenize. Then, the temperature was lowered to 60°C, and benzene was added to form a homogeneous solution. Next, 370 g of ethylaluminum sesquichloride was added dropwise at a predetermined temperature, and the mixture was stirred for 1 hour. A catalyst component was obtained by washing the generated precipitate with n-hexane. A portion of the obtained solid is dried to form a powder. This powder contained 11.0% by weight of Mg and 10.5% by weight of Ti. (2) Polymerization The above slurry containing 3 volumes of n-hexane was charged into an autoclave in the amount shown in Tables 1 and 2 as a solid component. A predetermined amount of the organic aluminum compound shown in Tables 1 and 2 was charged, and after the temperature was raised to a predetermined temperature, hydrogen was introduced. Next, ethylene or α-olefin was supplied at the same time as ethylene, and while supplying ethylene,
The polymerization reaction is carried out at the (hydrogen/ethylene) gas phase molar ratio shown in 2. The amount of polymerization reaction was determined based on the cumulative amount of ethylene supplied. When a predetermined yield was obtained, the supply of ethylene was stopped, the first stage polymerization was stopped, and the second stage polymerization was started. Here, hydrogen was purged, and α-olefin was then supplied, and while ethylene was being supplied, a constant pressure and constant temperature polymerization reaction was carried out at the (hydrogen/ethylene) gas phase molar ratio shown in Tables 1 and 2. Ta. The amount of polymerization reaction was determined based on the cumulative amount of ethylene supplied. The table below shows the results of measuring the physical properties of the obtained polymer.
Shown in 1 and 2.

【table】

【table】

【table】

〔Effect of the invention〕

By the production method of the present invention, it is possible to obtain a polyolefin which has excellent extrudability, excellent ballistic effect, and environmental cracking resistance, and which does not generate fish eyes.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing one embodiment of the present invention.

Claims (1)

[Scope of Claims] 1. 50 to 50% in a hydrocarbon solvent using a catalyst system consisting of a transition metal compound component and an organoaluminum compound.
During the homopolymerization of ethylene or the copolymerization of ethylene with other α-olefins at a temperature of 100°C, the reaction between an oxygen-containing organic compound of magnesium, an oxygen-containing organic compound of titanium, and an aluminum halide compound as transition metal compound components. Using a solid catalyst component as a product and an alkylaluminum sesquichloride as an organoaluminum compound, (a) the polymerization reaction is carried out in two stages, that is, in the presence of the reaction mixture obtained by polymerization in the first reaction zone. Second
(b) In one of the first and second reaction zones, polymerization is carried out in the presence of hydrogen in a molar ratio of 0.001 to 1.5 to ethylene in the gas phase. Polymer A with a viscosity average molecular weight of 150,000 to 1,000,000 was produced in an amount of 10% to 70% by weight of the total polymer production, and in the other zone, the molar ratio to ethylene in the gas phase was
Polymer B with a viscosity average molecular weight of 10,000 to 80,000 was polymerized in the presence of 1.5 to 15 hydrogen, and 90 of the total polymer production amount was obtained.
% to 30% by weight, and further (polymer A
(viscosity average molecular weight of polymer B)/(viscosity average molecular weight of polymer B) is 4 to 80, and (c) the melt index of all the polymers finally produced is less than 0.5 g/10 minutes. Method for producing polyolefin. 2. The production method according to claim 1, wherein the alkylaluminum sesquichloride is ethylaluminum sesquichloride.