JPH0550524B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for purifying polypropylene.
Specifically, the present invention relates to a method for producing polypropylene that does not cause coloring problems after granulation or molding. Prior Art When polyolefin is produced by polymerizing olefin using a Ziegler-Natsuta catalyst, catalyst residue remains in the polyolefin, which adversely affects the physical properties of the polyolefin, so many purification methods are known. Among them, the method of treating polyolefin with an OH-containing compound and then washing with water is an excellent method that can reduce the amount of catalyst residue in polyolefin to an extremely small amount. On the other hand, as the yield of polyolefin per catalyst has increased due to recent improvement in catalyst performance, it is necessary to simply treat with an OH-containing compound without washing with water, then simply filtration, static separation, countercurrent washing, etc. The amount of catalyst residue in the polyolefin obtained by simply separating the polyolefin is extremely small. Problems to be Solved by the Invention However, as mentioned above, polyolefin obtained without a water washing process has an extremely small amount of catalyst residue, but it cannot be granulated by adding additives such as phenolic antioxidants. There was a problem with coloring during storage when stored in such a state. The inventors of the present invention conducted extensive studies on methods for solving the above problems, and as a result, they discovered that the above problems could be solved by processing to satisfy specific conditions, and completed the present invention. Means for Solving the Problems That is, the present invention provides a polyolefin obtained by polymerizing using a catalyst consisting of at least titanium halide and magnesium halide and an organoaluminum compound selected from ethylene glycols and propylene glycols. This is a method for purifying a polyolefin, which comprises treating the polyolefin with a OH-containing compound to deactivate the catalyst, and then washing and/or drying the polyolefin until the OH-containing compound in the polyolefin becomes 300 ppm or less. In the present invention, the catalyst used in producing the polyolefin includes a highly active catalyst consisting of a combination of a titanium halide supported on a known magnesium halide and an organoaluminum, and the above-mentioned three components are used as the catalyst components. Any other components may be contained as long as they have the following components. These catalyst systems are preferably highly active so that the amount of catalyst residue in the polyolefin is 100 ppm or less even without complicated operations such as washing with water. What is important in the present invention is that the polyolefin thus obtained is treated with an OH-containing compound selected from ethylene glycols and propylene glycols, and then treated with a hydrocarbon compound etc. so that the OH-containing compound in the polyolefin is 300 ppm or less. cleaning and/or drying. Here, the OH-containing compounds include ethylene glycols such as ethylene glycol, ethylene glycol monoether, diethylene glycol, diethylene glycol monoether, triethylene glycol, and triethylene glycol monoether, or propylene glycol, propylene glycol monoether, and dipropylene glycol. ,
Propylene glycols such as dipropylene glycol monoether are exemplified as preferred compounds. After deactivating the catalyst with the above-mentioned OH-containing compound, the OH-containing compound reacts with the polyolefin.
Processed until it is below 300ppm. In this treatment method, polyolefin treated with an OH-containing compound is treated with propane, butane, hexane,
It is preferred to wash with an inert hydrocarbon compound such as heptane, benzene, toluene, or the olefin itself such as propylene, butene-1, and then dry. In addition, if the catalyst activity is sufficiently high and there is no need to remove the catalyst residue, simply removing the OH-containing
Heat, reduce pressure, and heat until the amount of the compound is 300 ppm or less.
Alternatively, it may be sufficient to simply air dry it. What is important is that
It is necessary to control the residual amount of OH compounds until it becomes 300 ppm or less; if it is more than 300 ppm, it will become colored during storage after granulation, making it unusable. Effect The cause of coloration during storage of granules is not clear;
The reason for the effect of the method of the present invention is not clear, but the OH-containing compound, titanium halide, magnesium halide, and antioxidant become colored substances through some kind of interaction, and one of the components of the production of colored substances is It is presumed that coloring no longer occurs by reducing the amount of the OH-containing compound below a certain level. Examples The present invention will be further explained with reference to Examples below. Examples 1 and 2 and Comparative Examples 1 and 2 A. Synthesis of catalyst components containing magnesium halide and titanium halide Vibration mill equipped with two crushing pots each having an internal volume of 900 ml and containing 80 steel balls with a diameter of 12 mm. Prepare. In this pot, under nitrogen atmosphere, 30 g of magnesium chloride and 3 ml of ethyl orthoacetate per pot.
6 ml of 1,2-dichloroethane was added and pulverized for 40 hours. By repeating this operation twice, 80 g of the pulverized product was brought into contact with 500 ml of titanium tetrachloride in a No. 2 round-bottomed flask under stirring at 80° C. for 2 hours, and then allowed to stand, and the supernatant liquid was removed. Next, 1 portion of n-heptane was added, the mixture was stirred at room temperature for 15 minutes, left to stand, and the supernatant liquid was removed. The washing operation was repeated seven times, and then 500 ml of n-heptane was further added to obtain a fixed transition metal catalyst slurry. B Polymerization Prepare an autoclave with an internal volume of 500, and
- A slurry of 128 ml of diethylaluminium chloride, 6 ml of methyl p-toluate, 4 ml of triethyl aluminum, and 3 g of the above catalyst was charged in 1 heptane, then 100 kg of propylene was charged, and 140 Nl of hydrogen was added.
The temperature was raised to .degree. C., and polymerization was carried out for 2 hours while charging propylene at 50 kg/h and triethylaluminum at 3 ml/h. Next, 3 charges of diethylene glycol monoisopropyl ether were charged to stop the polymerization reaction. C Half of the slurry obtained in the above polymerization reaction is
Unreacted propylene was directly purged, and one part of the resulting polypropylene powder was dried under normal vacuum (60 mmHg, 80°C, 10 hours (Comparative Example 1)),
One part was dried through fluidized aeration with nitrogen heated to 80°C.
It lasted for 10 hours (Example 1). For the remaining half, let it stand and remove the supernatant, then add 100kg of propylene, stir, let it stand and remove the supernatant twice, then purge the remaining propylene, and then add another part to the normal Drying under reduced pressure [60mmHg, 80℃, 5h (Comparative Example 2)], one part was
Drying under reduced pressure was repeated (after drying at 60 mmHg and 80°C for 5 hours, the operation of mixing the powder was repeated 5 times. (Example 2)) The total amount of dry propylene powder obtained in operation C was 38 kg. . D A phenolic antioxidant (2,6-ditertiary butyl 4-methylphenol) was added to the obtained dry powder at a weight ratio of 10/10,000 and calcium stearate at a weight ratio of 10/10,000, and the mixture was granulated using a known method, and the mixture was granulated at 30°C. After being stored for 3 months, the hue was visually evaluated. The results are shown in the table. Examples 3 and 4, Comparative Examples 3 and 4 Examples 1 and 2, except that triethylene glycol monomethyl ether was used as the OH-containing compound.
The same procedure as Comparative Examples 1 and 2 was carried out. The results are shown in the table. 【table】

Claims (1)

[Claims] 1 After deactivating the catalyst by treating a polyolefin obtained by polymerization using a catalyst consisting of at least a titanium halide, a magnesium halide, and an organoaluminum compound with an OH-containing compound selected from ethylene glycols and propylene glycols. , OH-containing compounds in polyolefin
A method for purifying polyolefin, which comprises washing and/or drying the polyolefin to a concentration of 300 ppm or less.