JPS599561B2 - Polypropylene purification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the purification of polypropylene obtained by using a stereospecific catalyst supported on anhydrous magnesium chloride.

A method for polymerizing propylene by using supported stereospecific catalysts is the subject of previous patents owned by the applicant.

According to one of these methods, the polymerization of propylene is carried out by a
) trihalide or tetrahalide of titanium supported on anhydrous magnesium chloride (halogen=C1, Br,
1) preferably TIC14, or together with an electron donating compound, more particularly ethyl benzoate, b) an electron donating compound,
In particular, it is carried out in the presence of a catalyst consisting of an aluminum-alkyl compound complexed with an organic ester such as ethyl anisate, ethyl benzoate, etc. Methods for making such supported catalysts are described in previous patents in the name of the applicant.

Polymerization can be carried out in the liquid phase in the presence or absence of a solvent.

Polymerization solvents include n-pentane, n-hexane, n-
Aliphatic or cycloaliphatic hydrocarbons can be used, such as heptane or cyclohexane. Examples of aluminum-alkyl compounds that can be used for the purposes of the present invention are:
Aluminum-triethyl, aluminum-tri-isobutyl, aluminum-tri-n-octyl, aluminum-diethyl monochloride, and the preferred compound is aluminum-triethyl.

The supported catalyst complex is of type T1Cl4.ethyl benzoate or type TiCl4.2.ethyl benzoate.

The metal-organic compound of the catalyst consists of aluminum-alkyl partially complexed with an electron-donating compound, and the molar ratio aluminum-alkyl/complexing agent can vary between 1 and 20.

The complexing agent giving the best results has proven to be ethyl anisate, and good results are obtained with ethyl benzoate. A preferred metal organic compound is an aluminum-triethyl/ethyl anisate complex in a molar ratio of 3. Polymerization methods in the presence of supported catalysts can achieve very high yields (19
50,000 to 200,0009 polymers),
Polymers with a low content of catalyst residues can be obtained.

In many cases, especially when it is desired to obtain polymers with high isotactic properties (in these cases the yield of polymer tends to be reduced), it is possible to It is advantageous to further reduce the content of such residues. The inventors unexpectedly discovered that the polymer, as a suspension in a hydrocarbon, was
an aliphatic alcohol having 1 to 10 volumes of hydrocarbon solvent, more specifically isopropyl or n-butyl alcohol. , preferably 2~
3 capacity? The amount of magnesium used in the treatment reduces the magnesium content in polypropylene produced in the presence of such supported catalysts by dissolving the catalyst residues present in the polymer. I admitted to getting it.

Treatment of the hydrocarbon suspension is carried out at a temperature in the range of 60-100° C. for a time sufficient to dissolve much of the catalyst residue.

Treatment is followed by centrifugation to remove both solvent and dissolved catalyst residue from the polymer. Hydrocarbons suitable for suspending polypropylene can be either aliphatic, cycloaliphatic or aromatic hydrocarbons.

The process of the invention is particularly applicable to polypropylenes obtained with catalysts supported on anhydrous magnesium halide in the presence of a hydrocarbon polymerization solvent. In this case, the polymerization slurry exiting the reactor is treated with alcohol. In addition to having a very low content of catalyst residues, the polymers thus obtained are able to remove much of the non-isotactic polymer that may be present as long as they are treated with alcohol under heating in the presence of a hydrocarbon solvent. It also exhibits high isotactic properties. Next, the present invention will be specifically explained with reference to Examples.

The examples show only one example, and the present invention is not limited thereto. Example 1 In this example, in accordance with the present invention, anhydrous MgCl2
Complexes supported on TlCl4, ethyl benzoate and 3
．． A catalyst consisting of AlEt3 partially complexed with ethyl anisate in a molar ratio of AlEt3/ethyl anisate equal to 14 was used.

To prepare the supported catalyst component, TlCl4 is introduced into a solution of ethyl benzoate in slight excess in heptane.

The precipitated complex was then washed repeatedly with heptane,
Then dry. Anhydrous M in an IBRATOM type crusher
Grind gCl2 for 50 hours.

The support thus produced is ground in the same grinder together with an appropriate amount of TiCl4/ethyl benzoate complex. The catalyst component thus obtained contains 3% titanium. The second catalyst component is prepared at the moment of its use in the polymerization by introducing ethyl anisate in the appropriate ratio into a solution of AlEt3 in heptane.

Therefore, the molar ratio of AlEt3/ethyl anisate is 3
．． It is 14. A complex is obtained. 0.61 in the given order to carry out the polymerization of propylene in an autoclave.
0) n-heptane, 0.12309 g of the supported catalyst component suspended in heptane together with a portion of the second catalyst component and finally the remainder of the second catalyst component. In this case, the second catalyst component is used in an amount corresponding to 1,1359 parts of AlEt3. The solvent is then saturated with propylene,
to a temperature of 60° C. and then the pressure was increased to 5.4° C. by continuously recombining the reacted propylene.
Maintain the pressure at atmospheric pressure for 5 hours. The polymerization slurry was then taken out from the reactor, stirred and added with 2% by volume of isopropyl.
Treat with alcohol at 900C for 1 hour. (The concentration of the slurry in the purification phase is in the amount of 3009/l). The product thus obtained is then centrifuged to remove the solvent and dissolved catalyst residues from the polymer, and finally the product is freed from the solvent by drying at 70° C. in a nitrogen atmosphere. A purified polymer of 1859 is thereby obtained. From the analysis carried out on the polypropylene sample thus obtained, it was found that the sample had Mg24PPm; Tl4PPm; Cll2
OPPm; total ash 0.07? It was confirmed that it contains.

The polypropylene separated from the slurry that was not treated with alcohol was Mgl32PPm:Tl2OPPm.
; Contained Cl45OPPm.

Examples 2 to 6 The operations related to these examples are as in Example 1.
The procedure was the same as that already described in , except that aromatic hexane was used instead of n-heptane as the polymerization solvent.

For further phase purification, n-butyl alcohol was used in the operations in Examples 2, 3 and 6. The operating conditions and results obtained are recorded in the following table.

Claims (1)

[Claims] 1. The polymer as a suspension in a hydrocarbon solvent is treated with an aliphatic alcohol having 3 to 8 carbon atoms, especially isopropyl alcohol or n-butyl alcohol.
(a) titanium trihalides or titanium tetrahalides or their complexes with electron donating compounds supported on anhydrous magnesium chloride, characterized in that they are treated in an amount of 1 to 10% by volume of the solvent; A process for the purification of polypropylene obtained by polymerization in the presence of a catalyst system consisting of a reaction product of aluminum-trialkyl partially complexed with an electron-donating compound.