JPS621642B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for stabilizing polyolefins obtained by polymerizing olefins using a catalyst comprising a transition metal halide and an organometallic compound.
In detail, polyolefin is treated as (A) cyclic ether and
(B) A method for stabilizing a polyolefin by removing the halogen content of the remaining catalyst and inactivating the remaining catalyst by contacting with a carboxylic acid. Obtained by polymerizing olefins such as ethylene, propylene, and butene using a catalyst system that combines a transition metal halide such as titanium, vanadium, and zirconium with an organometallic compound such as aluminum, zinc, and magnesium. The polyolefin contains each of the above catalyst components. Catalyst residues remaining in these polyolefins are heated when polyolefins are granulated and/or molded, which causes thermal deterioration of the polyolefins and corrodes equipment used during granulation and/or molding. Cause. Therefore, it is necessary to remove the residual catalyst from the polyolefin. A widely known method for removing catalyst residues remaining in polyolefins is to normally treat the produced polymer with alcohol to solubilize the remaining catalyst, and then extract it with water or hydrocarbons. However, such a method requires complicated equipment and processes to recover and reuse the alcohol and hydrocarbon containing the solubilized catalyst. On the other hand, due to recent improvements in catalyst performance, the production amount of polyolefin per catalyst has increased dramatically, so that the amount of catalyst residue remaining in the polyolefin has become relatively small. However, even a small amount of catalyst residue can cause corrosion of equipment during heat treatment during thermoplasticization of polymers, and the addition of ordinary stabilizers may result in poor thermal stability, resulting in poor thermal stability during granulation or molded products. Undesirable coloration may occur during production. On the other hand, when producing polyolefins by bulk polymerization or gas phase polymerization, which does not substantially use solvents, the product can be obtained in a dry state by simply removing excess monomer by evaporation using a simple device. In order to effectively bring out the advantages of the polymerization method, the process of removing catalyst residues involves, for example, adding appropriate additives to solubilize the catalyst residues,
There are methods to remove it by filtration or countercurrent cleaning. However, it is preferable not to carry out these operations over and over, and therefore a method for removing catalyst residues from a polyolefin containing catalyst residues in a dry state,
Alternatively, the development of a method to render it harmless is desired. Many examples of these methods are already known;
For example, there is a method of using an alkylene oxide and water in combination, as proposed in JP-A No. 49-87782 and JP-B No. 54-15315. However, in this method, the catalyst is not sufficiently stabilized, so it is necessary to add a larger amount of additive to avoid corrosion of the equipment. Furthermore, for reasons that are not clear, there are other problems such as the resulting product having an odor. In addition, as a method for treating polyolefins produced using a transition metal catalyst supported on a carrier such as magnesium chloride, Japanese Patent Laid-Open No. 52
A method of treatment with a carboxylic acid proposed in No. 69488 and JP-A No. 52-49285 is known. However, the polyolefin treated by this method has almost the same corrosivity as before treatment, and further has problems such as requiring special treatment. As a result of various studies, the present inventors discovered a method for removing and stabilizing the remaining catalyst residue by combining specific compounds and treating at a temperature below the melting point of polyolefin. I applied. However, in the above method, it is necessary to add an appropriate antioxidant and granulate the polyolefin before shipping it as a product. As a result of further studies, the present inventors have arrived at the present invention. It is an object of the present invention to provide a process for providing a stabilized polyolefin from a substantially dry polyolefin containing catalyst residues. In the present invention, a polyolefin obtained by polymerizing using a halogen-containing catalyst is treated with (A) a cyclic ether and (B) a carboxylic acid at a temperature equal to or higher than the melting point of the polyolefin in a state where the polyolefin is substantially dry. This method provides a stabilized polyolefin through contact treatment. Examples of the polyolefin in the present invention include homopolymers or mutual copolymers of α-olefins such as ethylene, propylene, butene-1, 4-methylpentene-1, and 3-methylbutene-1. Catalysts used in these polymerizations include halides of transition metals such as titanium, vanadium, and zirconium, or halides of these transition metals supported on halides and oxides such as magnesium, manganese, and aluminum; It is a combination of materials supported together with various organic compounds and an organometallic compound, preferably an organoaluminum compound. Furthermore, organic compounds containing N, O, P, etc. may be combined. When applying the method of the present invention, a preferred catalyst system is a highly active catalyst, and a catalyst system that provides 2000 g or more of polyolefin per 1 g of catalyst, especially a catalyst in which titanium halide is supported on magnesium oxide or halide. It can be preferably applied to polyolefins polymerized with a catalyst system consisting of an organoaluminum compound. The method for polymerizing α-olefin of the present invention includes:
Examples include a method using an inert hydrocarbon as a solvent, a bulk polymerization method using substantially no inert solvent, a gas phase polymerization method, and there are no particular limitations. Preferably, a solvent polymerization method using a relatively low boiling point solvent,
Alternatively, it is a bulk polymerization method or a gas phase polymerization method. The polyolefin obtained by the above polymerization method is subjected to the method of the present invention by removing unreacted monomers, solvents, etc. by means such as flashing, filtration, or centrifugation to obtain a powdered polyolefin. A stabilized polyolefin is obtained by contacting the polyolefin obtained by the above operation with (A) a cyclic ether and (B) a carboxylic acid at a temperature equal to or higher than the melting point of the polyolefin. Examples of the cyclic ethers (A) used in the method of the present invention include organic compounds containing an ethylene oxide group, a trimethylene oxide group, a tetrahydrofuran group, a dioxane group, and a trioxane group.
Specifically, compounds containing ethylene oxide groups such as ethylene oxide, propylene oxide, ethyl glycidyl ether, and butyl glycidyl ether, oxetanes such as trimethylene oxide, 2-methyl oxetane, and 2-butyl oxetane, tetrahydrofuran, and 3-methyl Examples include tetrahydrofurans such as tetrahydrofuran, dioxane, and trioxane, and those having a relatively low boiling point and having 2 to 10 carbon atoms are preferred. (B) Carboxylic acid has the general formula R-COOH
Monocarboxylic acids represented by (R: hydrocarbon residue having 1 to 39 carbon atoms), specifically compounds such as acetic acid, propionic acid, benzoic acid, stearic acid, or dicarboxylic acids containing two or more carboxyl groups ,
Tricarboxylic acids, specifically compounds such as oxalic acid, malonic acid, phthalic acid, maleic acid, terephthalic acid, and pyromellitic acid, as well as derivatives thereof, include acetoacetic acid, malic acid, tartaric acid, p-hydroxybenzoic acid, etc. is preferably used. In the method of the present invention, the above polyolefin powder is contacted with (A) cyclic ether and (B)
The carboxylic acid may be mixed in a closed container at a temperature equal to or higher than the melting point of the polyolefin, and a preferred treatment method is to mix at a temperature equal to or higher than the melting point, followed by treatment under reduced pressure. The most preferred form is to use a vented extruder and mix the mixture at a temperature above the melting point, then exhaust the vent with a vacuum pump and process under reduced pressure. The processing time above the melting point is about 0.1 minutes to 100 minutes, preferably about 1 minute to 10 minutes, and the processing temperature is above the melting point of the polyolefin to 400°C, preferably 180 to 280°C. It is best to go at the operating temperature. The usage ratio of (A) cyclic ether and (B) carboxylic acid varies depending on the compound used and cannot be specified, but
(A) The cyclic ether is used in an amount of 1 to 1000 times, preferably 10 to 100 times, by mole per 1 atom of the halogen atom remaining in the polyolefin, and (B) the carboxylic acid is used in an amount of 1 atom of the metal atom remaining in the polyolefin. 0.01 to 100 times the mole, preferably 0.1 to 10
It is common to use twice the mole amount. The presence of water during contact treatment is not particularly limited, and in certain combinations (B)
There are also combinations of compounds for which it is effective to have water present in an amount of 0.1 to 100 times the amount of carboxylic acid used. By using the method of the present invention, a stabilized polyolefin containing less halide can be obtained in the form of pellets in a single step, which is very useful for industrially producing polyolefins. The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto. Polymerization Example 1 Solid catalyst obtained by supporting titanium tetrachloride on magnesium chloride, triethylaluminum, diethylaluminum monochloride,
Polypropylene powder was obtained by carrying out bulk polymerization using a catalyst consisting of ethyl benzoate and using propylene itself as a solvent, and removing unreacted propylene by evaporation. The polypropylene powder thus obtained had Ti: 2ppm, Al: 186ppm, Mg:
It contained 20ppm and Cl: 210ppm. Examples 1 to 6, Comparative Examples 1 to 3 Using the powder obtained in Polymerization Example 1, an extruder SE-65B manufactured by Toshiba Machine Co., Ltd. (diameter: 65 mm, L/
D: 25, screw type: full flight), vent vacuum level: 40mmHg, cylinder temperature:
The treatment was carried out under constant conditions of 220 to 240°C, resin temperature: 235°C, and screw rotation speed: 80 rpm. Also table -
In addition to the additives shown in 1, 10g of each of calcium stearate and 2,6-ditertiarybutyl-4-phenol were added to 10,000g of powder. All extrusions were carried out at a rate of 60 kg/h. The contents of Ti, Al, Mg, and Cl in the pellets obtained by the above procedure were analyzed. In addition, 50g of pellets and a 2cm x 10cm x 0.1mm soft iron test piece were heated at 280℃ for 2 hours in a nitrogen atmosphere.
A corrosion test was conducted in which the test piece from which the polymer was removed was kept in a container at a temperature of 80° C. and a humidity of 90% or higher for 12 hours, and then dried. Furthermore, the sheet was irradiated with an aging test (JIS-7212) and a weather test (Sunshine Weather-Ometer (manufactured by Toyo Rika Kogyo Co., Ltd.), and the elongation in the tensile test (ASTMD638-64) decreased to 10% of the initial elongation. irradiation time). Table 1 shows the results.
Shown below. Polymerization Example 2 Polypropylene powder was obtained by polymerization in exactly the same manner as in Polymerization Example 1, except that a highly active solid catalyst containing titanium trichloride as a main component and a catalyst consisting of diethylaluminium chloride were used. This polypropylene
Contains Ti: 20ppm, Al: 122ppm, and Cl: 226ppm. Examples 7 and 8 Comparative Examples 4 and 5 The same tests as in Example 1 were conducted using the powder obtained in Polymerization Example 2, except that the additives shown in Table 2 were used. The results are shown in Table-2.

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Claims (1)

[Scope of Claims] 1 A polyolefin obtained by polymerizing using a halogen-containing catalyst is treated with (A) a cyclic ether and (B) at a temperature equal to or higher than the melting point of the polyolefin in a substantially dry state. A method for purifying polyolefin, characterized by contact treatment with a carboxylic acid. 2. The purification method according to claim 1, wherein the cyclic ether (A) is a compound containing an ethylene oxide group, a trimethylene oxide group, a tetrahydrofuran group, a dioxane group, or a trioxane group. 3. The purification method according to claim 1 or 2, wherein the carboxylic acid (B) is a carboxylic acid having 2 to 40 carbon atoms. 4. The purification method according to claim 1, 2, or 3, wherein the contact treatment at a temperature higher than the melting point is performed using a vented extruder.