KR100857963B1 - Polymerization method of polyethylene and ethylene copolymer for extrusion blow molding - Google Patents

Abstract

A method for preparing an ethylene polymer or ethylene copolymer for blow molding is provided to obtain an ethylene polymer or ethylene copolymer having excellent melt strength and appearance. A method for preparing an ethylene polymer or ethylene copolymer for blow molding uses two slurry phase polymerization reactors connected in series, wherein a first reactor is for preparing a low-molecular weight polymer and a second reactor is for preparing a high-molecular weight polymer. In the method, a solid complex titanium catalyst is used as a main catalyst, an organoaluminum compound is used as a cocatalyst, and ethyl aluminum sesquichloride is introduced in an amount corresponding to a molar ratio of 0.5-5.0 (aluminum/titanium in the main catalyst), and the main catalyst, cocatalyst and ethyl aluminum sesquichloride are introduced into the first reactor.

Description

Method for producing ethylene polymer and ethylene copolymer for blow molding {POLYMERIZATION METHOD OF POLYETHYLENE AND ETHYLENE COPOLYMER FOR EXTRUSION BLOW MOLDING}

The present invention relates to a method for producing a blow molding ethylene polymer or ethylene copolymer having a high melt strength and excellent appearance, and more particularly, to prepare a low molecular weight polymer in one reactor, and high in another reactor In series or parallel polymerization of ethylene using two slurry reactors for preparing a polymer having a molecular weight, a solid complex titanium catalyst is used as a main catalyst, an organoaluminum compound is used as a promoter, and further ethyl aluminum The present invention relates to a method for producing a blow molding ethylene polymer or ethylene copolymer having high melt strength and excellent appearance by adding sesquichloride in an amount of 0.5 to 5.0 based on aluminum / titanium molar ratio.

  Polyethylene blow molding containers are divided into small containers of less than 1ℓ, medium containers of 1 ~ 20ℓ, and large containers of more than 20ℓ, and household goods such as shampoo and rinse are mainly applied to small containers, and cooking oil, milk, Food products such as soy sauce are mainly applied, and chemicals such as chemicals are mainly applied to large containers.

Recently, the use of polyethylene terephthalate resin is increasing due to the tendency of the container centering on small and medium-sized containers, and as a result, the demand for improving the appearance quality of the conventional polyethylene container is gradually increasing.

Korean Patent No. 2003-0066409 is a hollow plastic polyethylene resin with excellent torsion strength, environmental stress crack resistance (ESCR resistance), impact resistance and appearance, and melt index (MFR, 2.16kg load) 0.1 ~ 2.0g / 10min, density A resin having a 0.957 to 0.967 g / cm 3 and melt index ratio (MFR21.6 / MFR2.16) of 200 or less is described.

However, polyethylene resins prepared in this manner do not satisfy the properties described above for all containers. For example, when the melt index ratio is too large or too small, problems arise in that the parison deflection and underweight occur due to the die line generation and the melt strength decrease when the medium container is applied.

Korean Patent No. 2004-7004825 is a resin that exhibits high environmental stress crack resistance and gloss resistance, and has a melt index of 0.5 to 2.0 g / 10 minutes, a density of 0.925 to 0.940 g / cm 3, and a molecular weight distribution of 2 to 7. A metallocene catalyst based polyethylene resin is described. However, the resin thus prepared is too narrow in molecular weight distribution and low in molecular weight, which is not suitable for forming a medium container.

The present inventors have conducted research to solve the above problems, as a result of using a solid complex titanium catalyst as a main catalyst in the preparation of ethylene polymer or copolymer, using an organoaluminum compound as a promoter, and further ethyl aluminum sesqui When chloride is applied in an amount of 0.5 to 5.0 based on the aluminum / titanium molar ratio, the present inventors have found that it is possible to prepare an ethylene polymer or an ethylene copolymer for blow molding that exhibits high melt strength and excellent appearance characteristics. .

In the present invention, in the ethylene polymerization or ethylene copolymerization, a low molecular weight polymer is produced in a first stage reactor and a high molecular weight polymer is produced in a two stage reactor. By using a solid complex titanium catalyst as a main catalyst, using an organoaluminum compound as a cocatalyst, and adding ethyl aluminum sesquichloride in an amount of 0.5 to 5.0 based on aluminum / titanium molar ratio, high melt strength and excellent The present invention relates to a method for producing an ethylene polymer or ethylene copolymer for blow molding having an external appearance.

The solid catalyst titanium catalyst, which is the main catalyst used in the method of the present invention, may be a titanium catalyst for ethylene (co) polymerization known in the art without particular limitation on its kind, and a preactivated solid complex titanium catalyst is particularly preferable. Do. Preferred preactivated solid complex titanium catalysts include those prepared by a process comprising the following steps:

(a) contacting a magnesium halide compound with an alcohol to prepare a magnesium compound solution;

(b) reacting the magnesium compound solution with a compound having a phthalic group represented by the following general formula (I), an ester compound having at least one hydroxy group, and a silicon compound having an alkoxy group represented by the following general formula (II) ;

C ₆ H _4- [CO ₂ -R] -a [CO ₂ -R '] ........ (I)

 [Where R, R 'is a hydrocarbon having 1 to 20 carbon atoms, alkyl, isoalkyl, tertiaryalkyl, alkenyl or aryl, which may or may not be the same as each other, and a is 2, 3, or 4 .]

R _n Si (OR ') _4-n ........... (II)

[Where R and R 'are hydrocarbons having 1 to 12 carbon atoms and n is 0 to 3]

(c) adding a mixture of a titanium compound and a silicon compound to the reactant to recrystallize the catalyst to prepare a solid titanium catalyst;

(d) The solid catalyst titanium catalyst is preactivated with a poly (hydrobakyl-aluminum oxide) compound.

Cocatalysts used in the process of the present invention include trialkylaluminums having 1 to 6 carbon atoms such as triethylaluminum and triisobutylaluminum as organoaluminum compounds.

The amount of ethyl aluminum sesquichloride used in the method of the present invention is 0.5 to 5.0 in terms of the molar ratio of titanium in aluminum / main catalyst in ethyl aluminum sesquichloride. If the aluminum / titanium molar ratio is less than 0.5, the molecular weight distribution is narrow, resulting in low melt strength and appearance defects such as die line. If the aluminum / titanium molar ratio exceeds 5.0, the molecular weight distribution is too wide, and the melt strength is lowered. , The appearance of poor appearance.

The ethyl aluminum sesquichloride is added together with the main catalyst and the cocatalyst during the polymerization reaction, and the two reactors are added together with the main catalyst and the promoter in the first stage reactor in series-linked polymerization, and in the case of parallel-linked polymerization, In this case, the main catalyst and the cocatalyst are added to both reactors.

In the method for preparing the ethylene copolymer of the present invention, comonomers having 4 to 6 carbon atoms, for example, 1-propene, 1-butene, 1-hexene, and the like may be used in 0.1 to 0.9 moles. In the method of introducing a comonomer in the polymerization step, a copolymer is prepared by adding a comonomer to a two-stage reactor in which a high molecular weight polymer is produced. In this case, when the comonomer is added to the first stage reactor in which the low molecular weight polymer is prepared, a low molecular weight ethylene copolymer is generated, which causes the degradation of environmental stress crack resistance, which is an important characteristic of the hollow molding container.

The reactor used in the present invention is used as a slurry reactor by connecting two reactors in series or in parallel. At this time, the solvent used as the diluent in the reactor uses an inert solvent such as hexane, heptane. The solid solution concentration of the polymer in the slurry at each stage is maintained at 100-400 g / liter-hexane.

The polymerization ratio of the low molecular weight polymer and the high molecular weight polymer produced in each stage reactor is preferably in the weight ratio of 45:55 to 55:45. If it is out of the above range, the molecular weight distribution is narrowed or widened to decrease the melt strength. It is not preferable to generate.

In the multi-stage polymerization reaction used in the present invention, it is preferable that the melt index of the low molecular weight polymer (190 ° C, 2.16Kg) is 5-30 g / 10 minutes in the first stage reactor in which the low molecular weight polymer is produced, and the melt index is 5 g / If it is less than 10 minutes, there is a problem that the molecular weight distribution is narrowed. If it exceeds 30 g / 10 minutes, the molecular weight distribution is too wide, which is not preferable.

The ethylene polymer and ethylene copolymer prepared by the process of the invention have a density of 0.95-0.97 g / cm 3. In addition, the ethylene polymer and ethylene copolymer prepared by the method of the present invention has a melt index (190 ° C., 2.16 Kg) in the range of 0.1 to 0.9 g / 10 min.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, these examples are for illustrative purposes only, and the present invention is not limited thereto.

Example  And Comparative example

[ Example  One]

Main catalyst  Produce

Step I: Preparation of Magnesium Solution

In a 1 liter reactor equipped with a nitrogen atmosphere mechanical stirrer, 9.5 g of MgCl ₂ and 500 ml of heptane were added and stirred at 500 rpm. Then, 72 ml of 2-ethylhexanol was added, the temperature was raised to 120 ° C., and reacted for 3 hours. . The homogeneous solution obtained after the reaction was cooled to room temperature.

II Step: with magnesium solution Phthalic  Catalytic reaction of a compound having a compound, an ester compound having at least one hydroxyl group, and a silicon compound having an alkoxy group

The magnesium solution obtained in step I was cooled to 70 ° C, and 4.6 ml of diisobutyl phthalate, 1.2 ml of 2-hydroxyethyl methacrylate and 10.0 ml of ethyl silicate were added thereto, and reacted for 1 hour.

III  Step: treatment of mixed solution of titanium compound and silicon compound

The solution prepared in step II was adjusted to room temperature, and a mixed solution of 90 mL of tetrachlorotitanium and 90 mL of tetrachlorosilicon was added dropwise for 2 hours. When the dropping was completed, the temperature of the reactor was raised to 80 ° C. over 1 hour and maintained for 1 hour. The reactor was cooled to room temperature, the stirring was stopped and the solution of the upper layer was separated and washed by injecting 400 ml of hexane until the unreacted free tetrachlorotitanium was removed. The titanium content of the prepared solid catalyst was 4.0 wt%.

IV  Step: catalyst Activation

The solid titanium catalyst prepared above was subdivided into 200 ml of hexane slurry so as to be 6 mmol / L on the basis of titanium atoms. The temperature of the solid titanium catalyst hexane slurry solution was lowered to 0 ° C., and 3.29 mL of a solution containing 10% methylaluminooxane dissolved in toluene by weight of aluminum was slowly injected into toluene while stirring. After the injection was completed, the solution temperature was raised to 20 ° C. and stirred for 5 hours to preactivate the solid titanium catalyst. After 5 hours, stirring was terminated and stored at -10 ° C.

polymerization

In the polymerization experiment, two reactors having a capacity of 90 liters in each stage were connected in series to polymerize. The ratio of polymerization amount in each stage was 50:50, and the ethylene input amount in each stage was 4 kg / hr. Slurry polymer polymerized in the first stage reactor was transferred to the two stage reactor by pressure difference to allow the polymerization to continue. The main catalyst prepared above was supplied at 0.1 mmol-Ti / hr in a single stage reactor, and polymerization was performed using triethylaluminum as a cocatalyst. In addition, ethylaluminum sesquichloride was added together with the main catalyst and the cocatalyst with a molar ratio of titanium in the aluminum / main catalyst of 2.0. As the comonomer, 1-butene was injected into the two-stage reactor so that the comonomer was introduced into the high molecular weight polymer portion. The polymerization temperature of the first stage reactor was 82 ℃, the reaction pressure was 8.0kg / ㎠, the polymerization temperature of the two stage reactor was 75 ℃, the reaction pressure proceeded to 2.5kg / ㎠. The slurry concentration was 160 g / liter-hexane in the first stage reactor and 140 g / liter-hexane in the two stage reactor. Slurry polymer after polymerization was separated by centrifugation, dried in a dryer to obtain a powder. The powdered polymer was then mixed with 1000 ppm of calcium stearate and 200 ppm of pentaerythritol tetrakis (3- (3,5-di-tetra-butyl-4-hydroxyphenyl) propionate) to granulate in pellet form in an extruder.

[ Example  2]

It was prepared in the same manner as in Example 1 except that the aluminum / titanium molar ratio of ethylaluminum sesquichloride was increased to 3.5.

[ Comparative example  One]

Prepared in the same manner as in Example 1 except that ethyl aluminum sesquichloride was not added.

[ Comparative example  2]

The preparation was carried out in the same manner as in Example 1, except that the aluminum / titanium molar ratio of ethylaluminum sesquichloride was adjusted to 6.0.

Physical properties of the pellet-like polymers prepared in Examples and Preparation Examples were measured and blow molded to evaluate container characteristics. The results are shown in Table 1 below.

Melt index: measured at 190 ° C. and 2.16 kg.

Melt Index Ratio: The melt index under the load of 21.6kg was divided by the melt index under the load of 2.16kg.

Molecular weight distribution: Measured by GPC (gel permeation chromatography), and expressed as the ratio of the weight average molecular weight and the number average molecular weight.

Melt strength: measured at a temperature of 210 ℃ using our melt strength measuring equipment (SMER).

Parison stability during blow molding: A 1.8 L cooking oil container was molded at a temperature of 200 ° C. in a blow molding machine having a 50 mm φ extruder, and the weight of the container was measured and the degree of appearance was evaluated.

Item Example 1 Example 2 Comparative Example 1 Comparative Example 2 1 stage reactor Polymerization temperature (℃) 82 82 82 82 Polymerization pressure (kg / ㎠) 8.0 8.0 8.0 8.0 Ethylene Flow Rate (kg / hr) 4.0 4.0 4.0 4.0 Hexane Flow Rate (kg / hr) 19.0 19.0 19.0 19.0 Type of promoter TEA ^{1 )} TEA TEA TEA EASC ^{2 )} (Al / Ti molar ratio) 2.0 3.5 0 6.0 Melt Index (g / 10min) 15 15 15 15 Two stage reactor Polymerization temperature (℃) 75 75 75 75 Polymerization pressure (kg / ㎠) 2.5 2.5 2.5 2.5 Ethylene Flow Rate (kg / hr) 4.0 4.0 4.0 4.0 Hexane Flow Rate (kg / hr) 18.0 18.0 18.0 18.0 Melt Index (g / 10min) 0.5 0.5 0.5 0.5 Polymer properties Melt Index (g / 10min) 0.35 0.35 0.35 0.35 Density (g / cm 3) 0.963 0.963 0.963 0.963 Melt Index Ratio 60 62 55 70 Molecular Weight Distribution (Mw / Mn) 12.5 12.8 11.5 13.5 Melt strength (mN) 154 140 115 125 Exterior Good Good Bad Bad Container weight (g) 86 85 80 82

(week)

1) TEA: triethylaluminum

2) EASC: ethyl aluminum sesquichloride

From the results of Table 1, in the preparation of ethylene polymers and copolymers using a titanium complex pre-activated as a main catalyst, an organoaluminum compound as a cocatalyst, the addition of ethylaluminum sesquichloride in an appropriate amount to blow molding and It was confirmed that the high melt strength and excellent appearance are important in the product.

As described above, using the ethylene polymer and copolymer prepared according to the method of the present invention exhibits excellent parison stability and appearance characteristics during the hollow molding of the medium container.

Claims (6)

In a series polymerization of ethylene using two slurry phase polymerization reactors for producing low molecular weight polymer in a first stage reactor and high molecular weight polymer in a two stage reactor, a solid complex titanium catalyst is used as a main catalyst, An aluminum compound is used as a promoter, and ethyl aluminum sesquichloride is added at a molar ratio of 0.5 to 5.0 based on the titanium in the aluminum / main catalyst, and the main catalyst, the promoter and the ethyl aluminum sesquichloride are used in a single stage reactor. Blow molding method for producing an ethylene polymer or ethylene copolymer for molding. delete delete The method of claim 1, wherein the polymerization ratio of the low molecular weight polymer produced in the first stage reactor and the high molecular weight polymer produced in the two stage reactor is 45:55 to 55:45 by weight ratio. Process for the preparation of coalescing. The method for producing an ethylene polymer or ethylene copolymer according to claim 1, wherein the melt index of the low molecular weight polymer in the first stage reactor in which the low molecular weight polymer is produced is 5 to 30 g / 10 minutes. The method of claim 1, wherein the melt index of the produced ethylene polymer or copolymer is 0.1 to 0.9 g / 10 minutes, and the density is 0.95 to 0.9 g / cm 3.