JPS6152165B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a technology for purifying polyolefin containing propylene or ethylene as a main component, and in particular, purifying polyolefin containing propylene or ethylene as a main component in a liquid hydrocarbon solvent having 3 to 4 carbon atoms using a Ziegler-Natsuta catalyst. Synthesized by polymerization, and using a countercurrent washing tower,
Suitable for use in purifying the above polyolefin by washing with a washing solvent mainly composed of a liquid hydrocarbon having 3 to 4 carbon atoms and removing catalyst residues and polymers soluble in the washing solvent. It is a great technology. Conventionally, a method for producing polyolefin using a Ziegler-Natsuta catalyst in a low-boiling hydrocarbon solvent having 3 to 4 carbon atoms is known, and in particular, a method for synthesizing polypropylene or a copolymer of ethylene and propylene using propylene itself as a solvent is known. The method of synthesizing polyethylene or a copolymer of ethylene and a small amount of propylene, butene, etc. in propane or butane is widely practiced industrially. Compared to the conventional suspension polymerization method in which polymerization is carried out using a relatively high-boiling saturated hydrocarbon solvent having 6 to 8 carbon atoms, the method of producing polyolefin in these low-boiling hydrocarbon solvents requires less polymerization solvent. Certain low boiling point hydrocarbon solvents have a high vapor pressure and are easily vaporized, so they have the great advantage that the polymer can be separated from the solvent by a simple operation such as flashing the polymerization slurry under atmospheric pressure. In addition, it is possible to increase the yield per catalyst by polymerizing in a low-boiling hydrocarbon solvent at relatively high pressure, and the yield per catalyst can be increased due to the significant improvement in the performance of recent catalysts. Due to the increase in the catalyst height, it is possible to reduce the amount of catalyst residue remaining in polyolefins, especially in polyolefins whose main component is ethylene, to the point where there are no problems with the quality of products in many fields. . However, when used in certain fields, such as food films, condenser films, etc., hydrocarbon solvent soluble polymers and catalyst residues (usually evaluated as ash, a non-combustible substance in polyolefins) are reduced to low levels. required to maintain. or,
For polyolefins whose main component is propylene,
Compared to polyolefins whose main component is ethylene, the yield per catalyst is small, so simply evaporating and removing the low-boiling point solvent will result in insufficient polymer color and weather resistance. If the stereoregularity of the polymer is low, or when the polymer is molded, the low molecular weight, low stereoregularity polymer will stand out on the surface of the molded product, causing problems such as stickiness. In order to solve these problems without losing the advantages of using a hydrocarbon solvent having 3 to 4 carbon atoms as a polymerization solvent, and furthermore, to solve the various problems mentioned above, a method using a Ziegler-Natsuta catalyst has been proposed. A polyolefin obtained by polymerizing in a hydrocarbon solvent with a low boiling point of 3 to 4 carbon atoms is first deactivated with an alcohol or an alkylene oxide, and then a catalyst with a carbon number of 3
The excellent It is possible to produce polyolefins with improved physical properties. (For example, Tokuko Sho 51-1274
No., JP-A-54-142290, etc.). However, in these methods, a much larger amount of low-boiling hydrocarbon solvent is used in countercurrent cleaning compared to the low-boiling hydrocarbon solvent used as the polymerization solvent, so it is difficult to recover the hydrocarbon solvent used in countercurrent cleaning. Usage is a big problem. As a method for recovering low-boiling hydrocarbon solvents used in countercurrent cleaning, it is naturally preferable to use a method that can increase the purity to the level used in the beginning. It is economical if purity can be achieved, and it is more preferable to do so. For example, a polymerization solvent and a countercurrent cleaning solvent are used separately, and for countercurrent cleaning, the volatile and nonvolatile components, catalyst residue and low molecular weight, low stereoregularity polymer, are simply separated. It is conceivable to use a liquid low-boiling hydrocarbon solvent by bringing the temperature of the volatile components obtained by the process below the boiling point. However, in this method, although the cause is not clear, the amount of catalyst residue in the purified polyolefin increases, and the effectiveness of cleaning in the countercurrent type cleaning tower is significantly lost. An object of the present invention is to provide a method for obtaining a polyolefin having excellent physical properties with very little catalyst residue and low molecular weight, low stereogenicity polymer by a relatively simple operation. As a result of examining various methods for solving the above problems, the present inventors have found a method of solving the above problems in an extremely simple manner by taking a specific method, and have completed the present invention. That is, the present invention uses a Ziegler-Natsuta catalyst to convert an unsaturated hydrocarbon monomer having 2 to 4 carbon atoms into a liquid hydrocarbon monomer having 2 to 4 carbon atoms in a liquid hydrocarbon solvent having 3 to 4 carbon atoms. The component is polymerized or copolymerized under conditions in which the component accounts for at least 90% by weight of the total polymer, and then an alcohol or glycol monoether having 1 to 15 carbon atoms, or an alcohol or glycol monoether having 2 carbon atoms is added.
A polyolefin slurry obtained by deactivating the catalyst with ~15 alkylene oxides is introduced into the upper part of the countercurrent washing tower, and at least 50% by volume from the lower part is a hydrocarbon solvent having 3 to 4 carbon atoms used as the polymerization solvent. In a method for obtaining purified polyolefin by extracting unreacted monomers with a washing solvent, catalyst residues dissolved in the solvent, and dissolved polymers,
Solvent and/or solvent from which polyolefin was removed by evaporation from polyolefin slurry extracted from the bottom.
Alternatively, the solution containing the catalyst residue and dissolved polymer extracted from the upper part is evaporated and the solvent excluding the catalyst residue and dissolved polymer is converted into a non-volatile component by at least carbonate of magnesium, aluminum, silicon, calcium or potassium. This is a method for purifying polyolefin, which is characterized in that a solvent treated in contact with a solid containing a hydroxide or oxide is used as a cleaning solvent that is introduced into the lower part of a countercurrent type cleaning tower. As the Ziegler-Natsuta catalyst used in the present invention, known α-based catalysts such as ethylene, propylene, butene, etc.
- Any material may be used as long as it is used for (co)polymerization of olefins or mixtures thereof and copolymerization with dienes, but there are no particular limitations, but the number of carbon atoms is 3 to 4.
Particularly effective are catalyst systems that provide the polyolefin in slurry form in a liquid hydrocarbon solvent. Specifically, titanium tetrachloride reduced with metallic aluminum or an organometallic compound, or a combination of a solid catalyst mainly composed of titanium trichloride, such as one further treated with an electron donor, and an organometallic compound, and various other catalysts. A solid catalyst in which a transition metal compound such as titanium tetrachloride is supported on a carrier such as a metal oxide, chloride, or hydroxide, or a transition metal compound such as titanium tetrachloride is supported on the above carrier treated with an organometallic compound. Preferred examples include combinations of solid catalysts and organometallic compounds and/or electron-donating compounds. As the hydrocarbon solvent having 3 to 4 carbon atoms used as a polymerization solvent in the present invention, it is also possible to use propylene, butene, etc., which are monomers that themselves polymerize, and in particular propylene homopolymers and copolymers of propylene and ethylene. When obtaining a polyolefin containing propylene as a main component, it is preferable to use propylene itself as a polymerization solvent. It is also possible to use a saturated hydrocarbon solvent that does not polymerize itself, and propane, butane, etc. are also preferably used. Examples of unsaturated hydrocarbon monomers having 2 to 4 carbon atoms used in the present invention include ethylene, propylene,
α-olefins such as 1-butene are preferred, and they may be homopolymerized or copolymerized. Also,
Furthermore, it is also possible to copolymerize other monomers with a large number of carbon atoms, such as olefins such as pentene, hexene, and octene, and dienes such as butadiene and hexadiene. It is of course possible to process it.
However, it is difficult to incorporate 10% by weight or more of these monomers with a large number of carbon atoms into the entire polymer. The process of deactivating the catalyst in relation to the present invention has the purpose of eliminating uncontrolled polymerization in the countercurrent washing tower, and here we use alcohols, glycol monoethers, alkylenes, etc., which have the effect of deactivating the catalyst in relatively small amounts. Oxides and the like are preferably used, and deactivating the catalyst with these compounds increases the effect of removing catalyst residues from the polyolefin. The alcohol and glycol monoether used here preferably have 1 to 15 carbon atoms, and specifically include monoalcohols such as methanol, ethanol, propanol, butanol, and hexanol, dialcohols such as ethylene glycol and butanediol, and ethylene. Examples include glycol monoethers such as glycol monomethyl ether, triethylene glycol monomethyl ether, and diethylene glycol monobutyl ether. Also,
The alkylene oxide preferably has 2 to 15 carbon atoms, such as ethylene oxide, propylene oxide, butyl glycidyl ether,
Examples include phenyl glycidyl ether. As the countercurrent type washing tower used in the present invention, it is possible to use a known one and is not limited to a special one, but it is generally a cylindrical pressure-resistant vessel with an inner diameter to height ratio of 1:2. ~1:50 is used. Furthermore, it is also possible to provide a stirrer in the column to make contact between the cleaning solvent and the polyolefin more efficient. The cleaning solvent introduced from the lower part of the countercurrent cleaning tower is not particularly limited as long as it has a low boiling point hydrocarbon solvent having 3 to 4 carbon atoms as its main component. That is, it suffices if it is liquid under the operating conditions of the countercurrent cleaning tower. In addition, it is preferable to use a liquid hydrocarbon solvent having 3 to 4 carbon atoms in which at least 50% by volume is used in the polymerization step, and 50% by volume or more is a liquid hydrocarbon solvent having 1 carbon number.
~2 hydrocarbon compounds or hydrogen will increase the operating pressure and will be less effective in removing soluble polymers, and if more than 50% by volume is a high boiling point hydrocarbon solvent with a carbon number of 5 or more, the product may deteriorate. This is undesirable because it complicates drying and recovery of the cleaning solvent extracted from the upper part of the countercurrent cleaning tower. In general, a dispersion solvent close to the composition of the slurry introduced into the countercurrent washing tower from the polymerization process is preferable for operation. The preferred flow rate of the liquid from the bottom to the top in the countercurrent cleaning tower is determined by the properties of the polyolefin slurry, particularly the shape and density of the polyolefin, the density of the cleaning solvent, etc., but is generally 0.01 to 5.
It is about cm/sec. The elements that characterize the present invention are the solvent used to remove the polyolefin by evaporation from the polyolefin slurry extracted from the lower part of the countercurrent washing tower, and/or the solution containing the catalyst residue and dissolved polymer extracted from the upper part of the countercurrent washing tower to be made non-volatile by evaporation. A solvent excluding the catalyst residue and dissolved polymer as a component,
After contacting with a solid containing at least a carbonate, hydroxide or oxide of magnesium, aluminum, silicon, calcium or potassium, the method is introduced in liquid form into the lower part of the countercurrent washing tower,
The recovered hydrocarbon solvent can account for 40% or more by volume of the cleaning solvent introduced into the lower part of the countercurrent cleaning tower. That is, the solvent recovered by evaporation from the solution containing the polyolefin inslurry, catalyst residue, and dissolved polymer discharged from the countercurrent washing tower is simply used as magnesium, aluminum, silicon, calcium, or potassium in liquid or gaseous form. Simply by contact treatment with solids containing carbonates, hydroxides, or oxides, the polyolefin can be purified to the extent that it can be reused as a cleaning solvent, and it can be reused without increasing the catalyst residue in the purified polyolefin. . The carbonates, hydroxides, or oxides of magnesium, aluminum, silicon, calcium, and potassium used here include various compounds.
Specifically, Mg(OH) ₂ , MgO, Al(OH) ₃ ,
_Al2O3 , _{SiO2 ,} Ca(OH) ₂ , CaO, KOH, _K2O ,
Examples include MgCO ₃ , Al ₂ (CO ₃ ) ₃ , CaCO ₃ , K ₂ CO ₃ , etc., which may be used alone or in combination, and
These eutectics are used. The shape of these compounds is not particularly limited, but spherical or cylindrical shapes with a diameter of 0.1 to 10 mm are usually used. The catalyst can be carried out in liquid or gaseous form using conventional solid-liquid or solid-gas contact equipment, and generally contains carbonates, hydroxides or oxides of the above-mentioned magnesium, aluminum, silicon, calcium and potassium. Preferably, the liquid recovered cleaning solvent is passed through a container filled with solids. Next, the present invention will be explained in detail with reference to the drawings.
This drawing simplifies the method of the present invention and shows only necessary parts, and the present invention is not limited to this example. It is also possible to add or delete substances. A polyolefin slurry that has undergone a polymerization process and a deactivation process (the deactivation process can of course be carried out in the countercurrent cleaning tower) is introduced into the upper part of the countercurrent cleaning tower 1 through a pipe 6. A hydrocarbon solvent recovered from the lower part of the countercurrent cleaning tower 1 through the following steps is introduced as a cleaning solvent together with a low-boiling hydrocarbon solvent newly added as needed. A solution in which catalyst residue and soluble polymer are dissolved is extracted from the upper part, introduced into flash tank 2 via piping 9, and separated from nonvolatile catalyst residue and soluble polymer. Purified polyolefin is extracted as a slurry from the lower part of the unidirectional flow cleaning tower 1,
It is separated into purified polyolefin and volatile components in a flash tank 5. The volatile components from the flash tanks 2 and 5 are cooled in the cooling device 3 and become liquid, and the solid-liquid contact is filled with solids containing carbonates, hydroxides, or oxides of magnesium, aluminum, silicon, calcium, and potassium. Through the device 4, if necessary, new hydrocarbon solvent is added or a portion is withdrawn, and the mixture is introduced into the countercurrent washing tower 1. The present invention is industrially significant in that it makes it possible to recover and reuse the solvent used for purification with a simple operation as a cleaning solvent introduced into a countercurrent type cleaning tower. The present invention will be explained below with reference to Examples. Example 1 (1) 20 g of a solid catalyst obtained by co-pulverizing 300 g of magnesium chloride, 166 g of a 1:1 complex of aluminum chloride and ethyl benzoate and supporting 1.5 g of titanium tetrachloride, 56 ml of ethyl benzoate, and diethyl aluminum chloride. Add 96ml and 80ml of triethylaluminum to 440kg of liquid propylene and polymerize, and after polymerization, add 100ml of isopropyl alcohol.
ml to deactivate the catalyst, polypropylene 200
A polypropylene slurry consisting of 240 kg of liquid propylene was obtained. (2) The polypropylene slurry obtained in (1) was fed into the upper part of the countercurrent washing tower with a diameter of 3 inches (7.62 cm) and a height of 5 m over 10 hours, and liquid propylene was fed into the lower part of the tower. The washed solution was withdrawn from the top at a rate of 41 kg per hour. A slurry consisting of 20 kg of polypropylene and 14 kg of propylene was extracted from the bottom of the unidirectional flow type washing tower. The slurry and washed solution extracted from the countercurrent washing tower were introduced into separate flash tanks to remove non-volatile components, and then cooled _to 10°C and _liquefied . ₁₆ CO ₃ (Estimated chemical formula, Kyowa Kagaku Kogyo Co., Ltd.'s Kiyoward 500 at 300℃
A cleaning solvent mainly composed of propylene was recovered at a rate of 45 kg per hour through a packed tower with a diameter of 10 cm and a height of 1 m filled with 3 kg of the cleaning solvent. After 2 hours, 31 kg of the recovered cleaning solvent was switched to the propylene for polymerization supplied to the lower part of the countercurrent type cleaning tower. During this cleaning, the ash content, titanium content, and chlorine content in the purified polypropylene obtained every 1 hour, 3 hours, 5 hours, and 9 hours from the start of operation of the countercurrent cleaning tower were analyzed, and the results are shown in the table below. Obtained. The table also shows the results of analyzing the amount of chlorine in the cleaning solvent.

[Table] Comparative Example 1 The same experiment as in Example 1 was conducted, except that a recovered solvent of Mg ₆ Al ₂ (OH) ₁₆ CO ₃ that did not pass through a packed column was used as the cleaning solvent, and the results shown in the table below were obtained.

[Table] Even though the amount of chlorine in the cleaning solvent was the same as in Example 1, the amount of ash and chlorine in the purified polypropylene increased over time. Example 2 An experiment similar to Example 1 was conducted, except that the solid introduced into the packed column was replaced with silica gel having a diameter of 3 mm, and the results shown in the table below were obtained.

[Table] Comparative Example 2 The same experiment as in Example 1 was conducted except that the solid introduced into the packed column was replaced with anhydrous calcium sulfate having a diameter of 3 mm. The results are shown in the table below.

[Table] This is an improvement over the case where no packed column is used at all, but the result is still not satisfactory. Example 3 (1) 8 g of a solid catalyst obtained by co-pulverizing 300 g of magnesium chloride, 58 g of a 1:1 complex of aluminum chloride and diphenyl ether, and 33 g of titanium tetrachloride.
220 kg of ethylene and 1-
Copolymerize 5 kg of butene, and after the pressure reaches approximately the vapor pressure of butane, deactivate the catalyst with 200 ml of triethylene glycol monomethyl ether, purge the gas layer, and produce 220 kg of polyethylene containing 1.5% by weight of 1-butene. A slurry consisting of 300Kg of butane was obtained. (2) The same procedure as in Example 1 was carried out, except that the slurry obtained in (1) above was used as the slurry introduced into the upper part of the countercurrent washing tower, and the solvent introduced into the lower part was replaced with butane. The ash content, titanium content, and chlorine content in purified polyethylene were analyzed, and the results shown in the table below were obtained.

[Table] Comparative Example 3 An experiment similar to Example 3 was conducted using a solvent mainly composed of butane, which was recovered without passing through a packed tower, as a cleaning solvent. The results are shown in the table below.

【table】 [Brief explanation of the drawing]

The drawing is an example of an explanatory diagram of an apparatus for carrying out the present invention, and in the drawing, 1... Countercurrent cleaning tower, 2... Flush tank, 3... Condenser, 4... Packed tower, 5... Flash tank, 6... Polyolefin slurry from the polymerization process, 7... Soluble polymer and catalyst residue,
8... Polyolefin product, 9... Gaseous solvent (including monomer).

Claims (1)

[Claims] 1 Using Ziegler-Natsuta catalyst with 3 or more carbon atoms
Polymerizing an unsaturated hydrocarbon monomer having 2 to 4 carbon atoms in a liquid hydrocarbon solvent in step 4 under conditions such that the unsaturated hydrocarbon component having 2 to 4 carbon atoms accounts for at least 90% by weight of the total polymer. Or copolymerize,
Next, a polyolefin slurry obtained by deactivating the catalyst with an alcohol or glycol monoether having 1 to 15 carbon atoms, or an alkylene oxide having 2 to 15 carbon atoms is introduced into the upper part of the countercurrent washing column, and at least 50% by volume is removed from the lower part. In a method for obtaining a purified polyolefin by extracting a cleaning solvent which is a hydrocarbon solvent having 3 to 4 carbon atoms used as the polymerization solvent, unreacted monomers, catalyst residues dissolved in the solvent, and dissolved polymers, The polyolefin was removed from the polyolefin slurry by evaporation from the polyolefin slurry extracted from the lower part, and/or the solution containing the catalyst residue and dissolved polymer extracted from the upper part was evaporated to remove the catalyst residue and the dissolved polymer as non-volatile components. The method is characterized in that a solvent treated in contact with a solid containing at least carbonate, hydroxide or oxide of magnesium, aluminum, silicon, calcium or potassium is used as a cleaning solvent to be introduced into the lower part of the countercurrent cleaning tower. A method for purifying polyolefin.