JPH1112336A - Production of block copolymer of propylene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out reutilization of recovered propylene and an inactive hydrocarbon compound and obtain a block copolymer in good productivity by using a specific catalyst system. SOLUTION: In producing polypropylene by initially polymerizing (D) propylene so that an amount of the resultant polypropylene is 40-95 wt.% based on total polymer by using a catalyst comprising (A) a transition metal catalyst component containing Mg and Ti, (B) an organoaluminum compound and (C) an alkoxysilicon compound and copolymerizing the component D with (E) ethylene so that an amount of the resultant polymer is 5-60 wt.% based on total polymer, (F) an inactive hydrocarbon compound is used as a diluent for the catalytic component and copolymerization of the component D with the component E is carried out in the presence of an alkylene glycol and a fraction after removing the component D as a low boiling point fraction is distilled in a first distillation tower in the presence of an excessive component B to remove a content having boiling point higher than the component F from the lower part of the distillation tower and a fraction extracted from the upper part of the distillation tower is introduced into a second distillation tower and low boiling point content is removed from the upper part and the component F is recovered from the lower part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a propylene block copolymer. More specifically, the present invention relates to a method comprising polymerizing using a specific catalyst and recovering an inert hydrocarbon compound by a specific method.

[0002]

2. Description of the Related Art Various methods are known for producing a block copolymer of propylene. Basically, a solvent polymerization method in which an inert medium is present, or a method in which a liquid monomer is used. It is manufactured by first copolymerizing propylene alone or with a small amount of other olefins by a bulk polymerization method, a gas phase polymerization method without a liquid medium, or the like, and then copolymerizing ethylene and propylene. It is well known that various catalysts can be used as the catalyst used in the polymerization, and a titanium halide-based catalyst that stereopolymerizes propylene,
A metallocene catalyst having a structure in which two ligands are bonded can be used. In particular, a catalyst system comprising a transition metal catalyst component containing magnesium and titanium and an organoaluminum compound is widely used because of its low cost and high performance. I have.

[0003]

The method of combining a transition metal catalyst component containing magnesium and titanium with a catalyst system composed of an organic aluminum compound and a bulk polymerization method or a gas phase polymerization method is excellent, and has high activity per catalyst and good physical properties. Block copolymer is obtained. In particular, in the bulk polymerization method, a block copolymer can be produced with high productivity, but a large amount of propylene needs to be recovered and reused. Therefore, the inert hydrocarbon compound used for diluting the catalyst component can be industrially economically recovered. However, if the distillation is carried out by a usual method, there is a problem that the performance of the catalyst is not sufficiently exhibited when the recovered propylene and the inert hydrocarbon compound are reused.

[0004]

Means for Solving the Problems The present inventors diligently studied a polymerization method which solved the above-mentioned problems and completed the present invention.

That is, the present invention provides a bulk polymerization method in which propylene itself is used as a liquid medium by using a reactor in which two or more polymerization tanks are connected, and a transition metal catalyst component containing magnesium and titanium, an organoaluminum compound, and an alkoxysilicon. Propylene is first polymerized by using a catalyst comprising a compound to produce polypropylene so as to be 40 to 95% by weight of the whole polymer, and then propylene and ethylene are copolymerized to make 5 to 60% by weight of the whole polymer. In a method for producing a block copolymer of propylene, which produces a copolymer such that an inert hydrocarbon compound is used as a diluent for a catalyst component, and copolymerization of propylene and ethylene is carried out in the presence of an alkylene glycol. From the fraction obtained by removing propylene as a low boiling point in the presence of excess organoaluminum compound, It recovered two high boiling fraction from the inert hydrocarbon compounds start with the recovery system consisting of a distillation column was removed from the distillation column bottom, the fraction withdrawn from the distillation column upper second
And removing the low-boiling components from the upper portion and recovering the inert hydrocarbon compound from the lower portion.

[0006]

The important point of the present invention is to use a catalyst system comprising a transition metal catalyst component containing a specific magnesium and titanium, an organic aluminum compound, and an alkoxysilicon compound as a stereoregular catalyst to be used.

[0007] The transition metal catalyst component containing magnesium and titanium can be produced by various methods, and when the transition metal catalyst component is produced, a magnesium salt which may be formed from metallic magnesium, magnesium oxide, or the like; Particularly preferred are magnesium halide and salts of titanium which may be produced when the transition metal catalyst component is produced, particularly those containing titanium halide. Here, examples of the magnesium halide include magnesium chloride, particularly anhydrous magnesium chloride.
Examples of the titanium halide include a titanium halide having at least one halogen atom or an alkoxyhalogenated titanium, preferably titanium chloride, and particularly preferably titanium tetrachloride. When producing a transition metal catalyst component containing magnesium and titanium, it is possible to use an electron-donating compound in combination, and as the electron-donating compound, usually ethers, esters, orthoesters, oxygen-containing compounds such as alkoxysilicon compounds, Or an amine,
Preferable examples include nitrogen-containing compounds such as amides, and alcohols, aldehydes, water and the like can also be used. Particularly preferred electron donating compounds include ethers and esters of aromatic dicarboxylic acids.

As the ether, those having various structures can be used, but compounds having two ether bonds in the molecule,
In particular, an aliphatic ether having three carbons between two ethers is preferable. Specifically, 2,2-diisobutyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane, 2,2- Bis (cyclohexylmethyl) -1,3-dimethoxypropane, 2-cyclohexyl-2-isopropyl-1,3-dimethoxypropane, 2-isopropyl-2-s-butyl-1,3-dimethoxypropane,
Examples thereof include 2,2-diphenyl-1,3-dimethoxypropane and 2-cyclopentyl-2-isopropyl-1,3-dimethoxypropane.

As the diester of an aromatic dicarboxylic acid, a diester of phthalic acid is particularly preferred. Specifically, an ester of phthalic acid and an alcohol having 1 to 12 carbon atoms can be preferably used, and dimethyl phthalate, diethyl phthalate, phthalate Dipropyl butylate, dibutyl phthalate, dioctyl phthalate, didecyl phthalate, diphenyl phthalate, dibenzyl phthalate, di-2-ethylhexyl phthalate, etc. Diesters such as ethylhexyl phthalate can also be used.

[0010] The simplest method of producing a transition metal catalyst component containing magnesium and titanium is to activate the titanium halide to a magnesium halide activated or unactivated by a variety of methods using the titanium halide as the transition metal catalyst component. Under certain conditions. Specific methods include magnesium halide and titanium halide, a method of co-milling an electron-donating compound if necessary, or a method of further heat-treating with an inert solvent. A method of dissolving in an organic solvent and then adding a titanium halide or the like to precipitate a magnesium halide and, if necessary, further supporting the titanium halide. A method in which the magnesium halide and the electron-donating compound are mixed and granulated, and then the titanium halide is added. And the like.

As the organoaluminum compound, trialkylaluminum, dialkylaluminum halide, alkylaluminum sesquihalide, and alkylaluminum dihalide can be used. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group. For example, chlorine, bromine and iodine are exemplified as halides. Particularly preferred is trialkylaluminum.

The alkoxysilicon compound used in the polymerization in the present invention preferably has a structure in which one to three alkoxy groups and one to three hydrocarbon residues having 1 to 12 carbon atoms are bonded to silicon. . As the hydrocarbon residue having 1 to 12 carbon atoms, an alkyl group, a cycloalkyl group,
Examples thereof include a phenyl group and a substituted phenyl group, and particularly preferred are an alkyl group and a cycloalkyl group. Examples of the alkyl group include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl groups, and examples of the cycloalkyl group include cyclopentyl, cyclohexyl, methylcyclohexyl, methylcyclopentyl, and norbornyl. Examples of the alkoxy group include methoxy, ethoxy, propoxy, butoxy, pentoxy, and phenoxy groups. The plurality of alkyl groups and alkoxy groups may be the same or different. Specifically, ethyltriethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, butyltriethylsilane, diethyldiethoxysilane, dipropyldimethoxysilane, dipropyldiethoxysilane, dibutyldimethoxysilane, dibutyldiethoxysilane, hexyltrisilane Examples include methoxysilane, hexyltriethoxysilane, dihexyldimethoxysilane, dihexyldiethoxysilane, dicyclohexyldimethoxysilane, dicyclohexyldiethoxysilane, dicyclohexyldipropoxysilane, dicyclohexyldibutoxysilane, dicyclohexylmethoxyethoxysilane, dicyclohexylmethoxyethoxysilane, and dicyclohexylmethoxypropoxysilane. .

Here, the molar ratio of titanium to magnesium in the transition metal catalyst component is generally about 1: 100 to 1: 3, and the ratio of electron donating compound to titanium is as follows: The molar ratio is generally about 1000: 1 to 1: 1. The ratio of the alkoxysilicon compound and the organoaluminum compound to titanium in the transition metal catalyst component is from 1: 1: 1-1: 100 in molar ratio.
Generally, the ratio of the electron donating compound to the organoaluminum is about 0: 1000 and about 1: 1 to 1: 100.

It is necessary that the polymerization be carried out by bulk polymerization both in the polymerization of propylene alone and in the copolymerization of ethylene and propylene, whereby the volumetric efficiency of the polymerization machine becomes extremely good. In addition, by using an alkylene glycol described below in the polymerization tank for performing the copolymerization, the proportion of the copolymerized portion can be strictly controlled, and the balance of physical properties can be made extremely excellent.

The preferred polymerization conditions of the bulk polymerization method using liquid propylene itself as a solvent employed in the present invention include a polymerization temperature of room temperature to 90 ° C. and a polymerization pressure of propylene which can be maintained in a liquid state under the polymerization conditions. Since the pressure is usually set so that a gas phase portion is present, it is automatically determined by the amount of a compound such as another monomer present in the polymerization system.

In a preferred embodiment of the present invention,
The homopolymerization of propylene is substantially carried out by a bulk polymerization method in a polymerization machine having two or more reactors, preferably two or more reactors connected to each other. Here, substantially propylene alone means, in the case of complete homopolymerization or copolymerization with other olefins such as ethylene, butene, and hexene, copolymerization is usually performed so that the rigidity of the final polymer is sufficient. Means that the polymerization is carried out so that the olefin content is 6% by weight or less. The polymerization of substantially propylene homopolymer is usually maintained at 90 to 40% by weight based on the whole polymer. If it exceeds 90% by weight, the improvement of impact resistance is insufficient, and %, The rigidity inherent to polypropylene is lost, which is not preferable.

In the present invention, further, the slurry is transferred from the final tank of the polymerization tank in which the homopolymerization was performed to the polymerization tank in which the copolymerization is performed, and the copolymerization is performed. Copolymerization may be carried out either batchwise or continuously, but it is more efficient to carry out it continuously.

The polymerization in the copolymerization tank is carried out at a reaction ratio of ethylene to propylene of 15/85 to 95/5 by weight, and part of ethylene is converted to another α-olefin such as butene, pentene or hexene. Can also be substituted. If the reaction ratio is out of this range, the effect of improving the impact resistance is insufficient. Of course, the copolymerization can be easily performed in multiple stages by changing the reaction ratio or the molecular weight.

In a more preferred embodiment, where the copolymerization is carried out continuously, the copolymerization is preferably carried out by connecting one or more reactors, preferably two or more reactors, in view of the physical properties of the polymer obtained. In the copolymerization section, the activity is controlled by adding a polyalkylene glycol to at least the first tank. Here, the polyalkylene glycol is a polyalkylene glycol such as polyethylene glycol or polypropylene glycol or a derivative thereof (one end or both ends are ether or ester bonds, etc.).

The polypropylene obtained by the method of the present invention is suitably used for various uses such as injection molding, extrusion molding and blow molding.

There are no particular restrictions on the molecular weight of the polymer in the substantially homopolymerized portion of propylene or in the copolymerized portion of ethylene and propylene, but the intrinsic viscosity measured at 135 ° C. in tetralin solution is 0.5 to 3 dl in the continuous polymerized portion. / g, about 0.5-20 dl / g in the copolymer part, 230 ° C as a copolymer
The melt flow index (hereinafter abbreviated as MI) measured under a load of 2.3 kg is preferably about 0.1 to 200 g / 10 min.

What is important in the present invention is that the polymerization is carried out also in the copolymerization section by the bulk polymerization method, so that unreacted propylene is recovered after polymerization, and when recovering unreacted propylene, an excess amount of an organoaluminum compound is present. The inert hydrocarbon compound used for dispersing the catalyst is separated from the portion obtained as a high-boiling fraction by first separating the high-boiling fraction from the inert hydrocarbon compound in a separation zone comprising two distillation columns. An object is to obtain a recovered and purified inert hydrocarbon compound by removing a low boiling point fraction.

"Excess of the organoaluminum compound" means that the number of moles of the organoaluminum compound is larger than the total number of moles of all the electron donating compounds. In this case, as described above, the excess amount of organoaluminum is used and sent to the inert hydrocarbon recovery step as it is, and when a deactivator such as a lower alcohol is added, an equimolar amount or more of the deactivator used is used. Preferably, 1.5 mol times or more of the organoaluminum compound is added in advance. The step of recovering the inert hydrocarbon compound will be described with reference to FIG. In the presence of excess organoaluminum, the residual component from the polymer removal from the polymer is separated in a distillation column 1 from a low boiling point composed of propylene and ethylene, and is taken out from the top of the column. The low-boiling components are separated in the distillation column 2 into a fraction composed of propylene and ethylene and a propylene fraction, and are taken out from the top and bottom, respectively.
In the recovery of propylene, the recovery energy efficiency is good by separating and recovering a propylene / ethylene mixture fraction and a propylene fraction that can be used for copolymerization of ethylene and propylene, and can be used for polymerization. It can be separated and recovered into propylene, a mixture of propylene and ethylene, and an inert hydrocarbon compound.

The distillate from the bottom of the distillation column 1 from which the low-boiling components have been removed is introduced into a recovery system composed of the distillation columns 3 and 4 and treated. That is, the fraction from the bottom of the distillation column 1 is sent to the distillation column 3, and a high-boiling component is taken out of the inert hydrocarbon compound from the bottom, and an inert hydrocarbon compound and a low-boiling component are taken from the top of the column. The fraction consisting of The withdrawn fraction at the top is sent to the distillation column 4, where low boiling components are recovered from the top and inert hydrocarbon compounds are recovered from the bottom.

[0025]

The present invention will be further described with reference to the following examples. In Examples and Comparative Examples, the physical properties of the polymers were measured as follows.

The product powder obtained by the polymerization was added with 0.1% by weight of a phenolic stabilizer and 0.1% by weight of calcium stearate, mixed with a Henschel mixer, and then pelletized with a 50 mmφ single screw extruder at a cylinder temperature of 240 ° C. A test piece was prepared from the obtained pellet using an injection molding machine (J100E, manufactured by Nippon Steel Works) with a mold clamping pressure of 100 t at an injection temperature of 270 ° C and a mold temperature of 50 ° C. The measurement of each physical property was performed as follows.

Melt flow index (g / 10min): ASTM D1238 (230 ° C) Tensile yield strength (kgf / cm2): ASTM D638 (23 ° C) Izod (with notch) Impact strength (kgf · cm / cm): ASTM D256 -56 (23 ° C, -10 ° C) Dupont impact strength (kgf · cm / 1/2 "φ): MI was measured based on JIS K6718 (23 ° C, -10 ° C) with a load of 2.16 kg. The numbers were 135 ° C. tetralin solution and the ethylene content was measured by infrared absorption spectroscopy.

Example 1 (Production of a transition metal catalyst component) A vibration mill equipped with four 4 L (liter) grinding pots containing 9 kg of steel balls having a diameter of 12 mm is prepared. 300 g of magnesium chloride, 115 ml of diisobutyl phthalate, and 60 ml of titanium tetrachloride were added to each pot in a nitrogen atmosphere, and pulverized for 40 hours.

5 g of the above co-ground product was placed in a 200 L flask, 100 ml of toluene was added, and the mixture was stirred at 114 ° C. for 30 minutes, and then allowed to stand to remove the supernatant. Then n-heptane 100
The solid content was washed three times with 20 ml at 20 ° C. and dispersed in 100 ml of n-heptane to obtain a transition metal catalyst component slurry. The resulting transition metal catalyst component contained 1.8% by weight of titanium and 18% by weight of diisobutyl phthalate.

(Pretreatment of transition metal catalyst component) 100 g of the above transition metal catalyst component, 12.9 g of triethylaluminum,
100 L of heptane was inserted into an autoclave having an internal volume of 200 L. Then, 1000 g of propylene was inserted while maintaining the internal temperature at 10 ° C., and after stirring for 30 minutes, 7.1 g of titanium tetrachloride was charged to obtain a pretreated catalyst component slurry.

(Polymerization reaction) In a first polymerization tank having an inner volume of 1000 L, 131 kg / hour of propylene, 1.0 g / hour of a transition metal catalyst component subjected to the above pretreatment as a catalyst, 19.5 g / hour of triethylaluminum, cyclohexylmethyldimethoxy 0.8 g / hour of silane is continuously supplied, and the slurry obtained by polymerization is continuously sent to a second polymerization tank having an internal volume of 500 L,
Further polymerized. The temperature of the first polymerization tank was 75 ° C., and hydrogen was supplied so that the hydrogen concentration in the gas phase became 1.6 mol%. Second
Propylene is supplied to the polymerization tank at a rate of 40 kg / hour, and the temperature is 7
Hydrogen was supplied at 2.5 ° C. so that the hydrogen concentration in the gas phase was adjusted to 1.3 mol%.

At the time when the first stage polymerization was completed, the average reaction amount was 43000 g-PP / g transition metal catalyst component. The slurry in the second polymerization tank was sampled, and the limiting viscosity number (hereinafter abbreviated as [η]) of the polymer was measured.
It was 39 dl / g. The slurry exiting the second polymerization tank has an internal volume
It was supplied to a 500 L third polymerization tank.

In the third polymerization tank, diethylene glycol ethyl acetate as an ether is used as the T in the transition metal catalyst component.
It was added at a rate of 133 mol times per i component.

The temperature of the third polymerization tank is 52 ° C. and propylene is 20
The polymerization was performed by feeding ethylene and hydrogen so that the polymerization pressure was 28.5 kg / cm2-G and the hydrogen concentration was 1.3 mol%. The slurry that has left the third polymerization tank has an internal volume of 500 L
To the fourth polymerization tank. The temperature of the fourth polymerization tank is 50 ° C., propylene is supplied at 15 kg / hour, and the pressure is 27.5 kg / cm 2 -G,
Polymerization was performed by supplying ethylene and hydrogen so that the hydrogen concentration became 1.3 mol%. After the unreacted monomer was removed from the slurry leaving the fourth polymerization tank, the polymerization powder was recovered. The powder was obtained at 51 kg / hour and dried at 80 ° C. and 70 mmHg for 10 hours to obtain a product. [Η] of the product was 1.67 dl / g and ethylene content was 7.6% by weight. The bulk specific gravity of this powder is 0.37g
/ Cc and the fluidity was good. The proportion of the copolymer part calculated from the analysis value of magnesium in the powder was 15% by weight. After adding a stabilizer to this powder and performing heat-melt granulation, the physical properties were measured.The melt flow index (g / 10min) was 7.9, and the tensile yield strength (kgf / cm2) was 276.
Izod (with notch) Impact strength (kgfcm / cm) is 23 ℃,
10.8 and 4.4 at -10 ° C, DuPont impact strength (kgf
m / 1/2 "φ) were 73 and 50 at 23 ° C and -10 ° C, respectively.

The recovery of the unreacted monomer and the inert hydrocarbon compound after recovery of the polymerization powder was carried out using the apparatus shown in FIG. The mass balance is presented according to the line in FIG.

Each of the fractions thus obtained was compared with pure propylene and pure heptane used in the above-mentioned polymerization.

In a 5 L autoclave, propylene was added.
1.5 kg, transition metal catalyst component 15 m suspended in purified heptane
g, 0.2 ml of triethylaluminum, 0.10 ml of cyclohexylmethyldimethoxysilane and 1.1 NL of hydrogen were added, and the temperature was increased to 70.
After polymerization at 2 ° C. for 2 hours, the weight of the polypropylene was measured. The activity of the catalyst produced using purified propylene was 46400 g-PP / g. It was a PP / g transition metal catalyst component. On the other hand, heptane recovered as heptane used for washing the catalyst component when synthesizing the transition metal catalyst component was used, and the polymerization was performed in the same manner as the comparison of propylene described above. Was 47100 g-PP / g transition metal catalyst component, whereas 46700 g-PP
/ G transition metal catalyst. Comparative Example 1 Heptane was recovered by a method of first removing a low-boiling fraction and then removing a high-boiling fraction (in FIG. 1, the order of the distillation column 3 and the distillation column 4 was reversed). When compared in the same manner as in Example 1, only the activity of 31400 g-PP / g transition metal catalyst was obtained.

[0038]

By carrying out the method of the present invention, it is possible to efficiently produce a propylene block copolymer, which is extremely valuable industrially.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an example of the present invention, a distillation step for recovering propylene and heptane from an evaporated matter from which polypropylene has been removed.

Continued on the front page (72) Inventor Harima, 1-6-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Chemicals Co., Ltd.

Claims (2)

[Claims] 1. A bulk polymerization method using propylene itself as a liquid medium, comprising a transition metal catalyst component containing magnesium and titanium, an organoaluminum compound, and an alkoxysilicon compound using a reactor having two or more polymerization tanks connected to each other. First, propylene is polymerized using a catalyst to obtain 40 to 9 of the total polymer.
5% by weight of polypropylene is produced, and then propylene and ethylene are copolymerized to obtain 5 to 60% of the total polymer.
In a method for producing a propylene block copolymer in which a copolymer is produced in an amount of 1% by weight, an inert hydrocarbon compound is used as a diluent for a catalyst component, and propylene and ethylene are copolymerized in the presence of an alkylene glycol. In the presence of an excess of an organoaluminum compound, an inert hydrocarbon compound is recovered from a fraction obtained by removing propylene as a low-boiling fraction in a recovery system comprising two distillation columns, first having a higher boiling point than the inert hydrocarbon compound. From the lower portion of the distillation column, and the fraction extracted from the upper portion of the distillation column is introduced into a second distillation column to remove low-boiling components from the upper portion and to recover an inert hydrocarbon compound from the lower portion. A method for producing a block copolymer. 2. The method according to claim 1, wherein the transition metal catalyst component containing magnesium and titanium is a titanium halide supported on a magnesium halide.