JPS62162B2 - - 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 again, and it is therefore desirable to develop a method for removing catalyst residues from a dry polyolefin containing catalyst residues or a method for rendering them harmless. Many examples of these methods are already known;
For example, there is a method of using alkylene oxide and water in combination, as proposed in JP-A-49-87782. However, this method does not stabilize the catalyst sufficiently, and it is necessary to add a larger amount of additives 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 polyolefin produced using a transition metal catalyst supported on a carrier such as magnesium chloride, a method using a carboxylic acid proposed in JP-A-52-69488 and JP-A-52-49285 has also been proposed. There are known ways to treat it. 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 catalyst residues remaining in polyolefin by combining specific compounds, and completed 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 polymerization using a halogen-containing catalyst is treated with (A) a cyclic ether and (B) a carboxylic acid at a temperature below the melting point of the polyolefin in a substantially dry state. 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. A preferred catalyst system for applying the method of the present invention is a highly active catalyst, and is a catalyst system that provides 2000 g or more of polyolefin per 1 g of catalyst, especially a catalyst system 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 a catalyst and 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, or a gas phase polymerization method, but there are no particular limitations. Preferably,
These include a solvent polymerization method using a solvent with a relatively low boiling point, a bulk polymerization method, and a gas phase polymerization method. The polyolefin obtained by the above polymerization method is made into a powdered polyolefin by removing unreacted monomers and solvents by means such as flashing, filtration, or centrifugation.
The method of the invention is then applied. A stabilized polyolefin can be obtained by contacting the polyolefin obtained by the above operation with (A) a cyclic ether and (B) a carboxylic acid at a temperature above room temperature and below the melting point. At temperatures below room temperature, the reaction between the residual catalyst in the polymer and the treating agent does not proceed sufficiently, making it difficult to remove the halogen and deactivate the catalyst. Furthermore, at temperatures exceeding the melting point of the polymer, the polymer melts and insufficient contact with the processing agent occurs. 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-methyltetrahydrofuran. Examples include tetrahydrofurans such as dioxane, trioxane, etc., 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, are mentioned, and malic acid, tartaric acid, p-hydroxybenzoic acid, etc. are preferably used. It will be done. In the method of the present invention, the above polyolefin powder is contacted with (A) cyclic ether and (B)
It is sufficient to place the carboxylic acid in a closed container and contact the polyolefin at a temperature below the melting point of the polyolefin. In particular, when (A) cyclic ether and (B) carboxylic acid are compounds with a relatively high boiling point, they must be thoroughly mixed at a relatively low temperature. Preferably, the temperature is then increased for further processing. It is preferable to carry out the treatment at a high temperature, above room temperature and below the melting point of the polyolefin, since a sufficient effect can be obtained in a relatively short period of time. Specifically, it is preferable to carry out the reaction at a temperature between 70° C. and the melting point of the polyolefin. The contact treatment time varies depending on the compound used and the contact treatment temperature and cannot be specified, but 5 minutes to 1 hour is usually sufficient. There are no particular restrictions on the equipment used during the contact treatment, and any equipment that can sufficiently mix the three components described above may be used. The usage ratio of (A) cyclic ether and (B) carboxylic acid varies depending on the compound used and cannot be specified, but (A) cyclic ether is 1 atom per halogen atom remaining in the polyolefin.
~1000 mol times, preferably 10 to 100 mol times,
The carboxylic acid (B) is generally used in an amount of 0.01 to 100 moles, preferably 0.1 to 10 moles, per 1 atom of metal atom remaining in the polyolefin. The presence of water during contact treatment is not particularly limited;
In certain combinations, (B) for the amount of carboxylic acid used.
There are some compound combinations for which the presence of 0.1 to 100 molar amounts of water is effective. After the above contact treatment, remove excess (A) cyclic ether and (B) carboxylic acid by performing a reduced pressure treatment or passing nitrogen through the mixture, or add a known appropriate stabilizer and perform a granulation operation. gives even more favorable results. By using the method of the present invention, a stabilized polyolefin can be obtained with a simple operation,
This is very meaningful 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 a composition as shown in Comparative Example 1 in Table 1 and contained Ti, Al, Mg, and Cl. Examples 1 to 6, Comparative Examples 1 to 3 Additives in the amounts shown in Table 1 were added to 3 kg of the powder obtained in Polymerization Example 1, and the mixture was treated under the treatment conditions shown in Table 1 while stirring in a closed container. Thereafter, excess additives were removed by flowing nitrogen at 1/min at the treatment temperature, and Ti, Al, Mg, and Cl were measured. Furthermore, 50 g of the treated powder was brought into contact with a 2 cm x 10 cm x 0.1 mm soft iron test piece for 2 hours at 280°C in a nitrogen atmosphere, and then the test piece with the polymer removed was heated to a temperature of 80°C and a humidity of over 90%. Corrosion tests were conducted by holding the samples in a container for 12 hours and then drying them. Note that the corrosion area in the test results represents the ratio of the rusted or cloudy area to the total surface area. To the remaining powder, 3 g of calcium stearate and 3 g of 2,6-ditertiarybutyl-4-methylphenol were added, mixed, granulated, and subjected to aging test (JIS-7212) and weather resistance test (Sunshine Weather-Ometer). Table 1 shows the results of a tensile test (ASTMD638-64) of the irradiation time when the elongation decreased to 10% of the initial elongation. Comparative Example 4 10 g of methanol was added to 3 kg of the powder obtained in Polymerization Example 1, stirred at 50° C. for 30 minutes, filtered and dried to obtain polypropylene powder. This powder was subjected to the same corrosion test, aging, and weather resistance test as in Example 1. The results are shown in Table 1. 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 had a composition as shown in Comparative Example 5 in Table 2, including Ti, Al,
Contains Mg and Cl. Examples 7 and 8 Comparative Example 6 The same tests as in Example 1 were conducted using the powder obtained in Polymerization Example 2 under the conditions shown in Table 2. 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 heated to a temperature above room temperature and below the melting point in a state in which the polyolefin is substantially dry, to prepare (A) a cyclic ether and ( B) A polyolefin purification method 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.