JPS62185703A - Method of purifying polypropylene - Google Patents

Abstract

PURPOSE:To obtain PP of good quality in a high yield without causing any troubles such as the clogging of a production line, by introducing a PP slurry formed by a bulk polymn. into the top of a countercurrent scrubber and scrubbing it with a scrubbing liquid propylene by introducing the liquid propylene from the bottom of the scrubber while controlling the temp. of the liquid propylene at the time of the introduction thereof and after scrubbing. CONSTITUTION:Propylene is polymerized by a bulk polymn. method using propylene itself as a liquid medium. If desired, a catalyst is deactivated and solubilized by using alcohols. The resulting PP slurry is introduced into the top of a countercurrent scrubber. A scrubbing liquid propylene whose temp. is controlled to a temp. lower by 1-80 deg.C than that of the PP slurry (e.g., 0-60 deg.C) is introduced into the scrubber from the bottom thereof and brought into countercurrent contact with the slurry. After scrubbing, the scrubbing liquid is heated to a temp. which is not lower by 20 deg.C than that of the introduced slurry and withdrawn from the top of the tower. The washed slurry is taken from the bottom of the tower to obtain PP powder.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for purifying polypropylene.

Specifically, the present invention relates to a method for purifying polypropylene by countercurrent washing polypropylene obtained by bulk polymerization using a specific method.

BACKGROUND TECHNOLOGY The method of polymerizing stereoregular polypropylene by polymerizing propylene alone or propylene and other α-olefins using a bulk polymerization method using propylene itself as a liquid medium is already well known, and recent catalysts As performance improves, polypropylene with high stereoregularity and catalytic light can be obtained in high yield, making it possible to separate polypropylene and commercialize it by simply evaporating off unreacted monomers. . However, for certain applications such as films, it is necessary to remove catalyst residues or low crystallinity, low molecular weight polymers. For this purpose, a method using a countercurrent cleaning tower is advantageous because of its good cleaning efficiency and simple structure.

Problems to be Solved by the Invention Although the method using a countercurrent washing tower is a preliminary and effective method, in order to meet the demand for higher quality products on an industrial scale, it is necessary to In order to increase the extraction efficiency of the countercurrent washing tower, it is common practice to coexist a hydrocarbon compound with a high boiling point or to operate the countercurrent washing tower at a relatively low temperature. (For example, JP-A-48-9
3685, Special Publication No. 53-4107. JP-A-61-270
8. Unexamined Japanese Patent Publication No. 61-202, etc. ) According to the above-mentioned method, high-quality polypropylene can be obtained in an extremely high yield, and it is an industrially desirable method that is superior to the gas phase method in terms of quality and superior to the solvent method in terms of yield. When a current washing tower is operated for a long period of time, there is a problem in that the upper part of the countercurrent washing tower, especially the cleaning liquid piping, gets clogged.

Means for Solving the Problems The present invention has been completed by intensive study on methods for solving the above problems.

That is, in the present invention, a polypropylene slurry obtained by polymerization using a bulk polymerization method using propylene itself as a medium is charged into the upper part of a countercurrent washing tower, washed propylene is introduced from the lower part of the tower, and the washed polypropylene is introduced from the lower part of the tower. In the method of purifying polypropylene by extracting the washing liquid from the upper part of the tower, the temperature of the washing propylene introduced from the lower part of the tower is lower than that of the polypropylene slurry introduced into the countercurrent washing tower, and the washing liquid extracted from the upper part of the tower is introduced. This is a polypropylene purification method characterized by heating the slurry so that the temperature does not drop below 20°C.

In the method of the present invention, there are no limitations on the conditions, polymerization catalyst, polymerization conditions, post-treatment conditions, etc. for producing a polypropylene slurry, and known methods can be employed. For example, the catalyst may be titanium trichloride obtained by reducing titanium tetrachloride with hydrogen, metals, organic aluminum, etc., or titanium trichloride further activated by pulverization, co-pulverization, contact treatment with oxygen-containing compounds, etc., or halogenated titanium. A so-called highly stereoregular catalyst system consisting of a titanium halide, preferably titanium tetrachloride, supported together with an oxygen-containing compound or the like on a carrier such as magnesium, and an organometallic compound, especially an organoaluminum compound, is used as a catalyst system. Used with regularity improver.

In the present invention, the bulk polymerization method using propylene itself as a liquid medium refers to a relatively high boiling point hydrocarbon compound such as pentane, hexane, heptane, benzene, toluene, ethylbenzene nonanedecane, or a mixture thereof. For example, conditions in which other α-olefins such as ethylene, butene-1, heptene-1, hexene-1, etc. are present in an amount that does not lead to It also includes random copolymerization or block copolymerization with other α-olefins.

The polymerization temperature is room temperature to 90°C. The polymerization pressure is the polymerization temperature and the above-mentioned hydrocarbon compound or other α-
It is determined by the amount ratio of olefin, hydrogen, etc. used as a molecular ffi regulator in the system.

The polypropylene slurry obtained by the above method is treated with alcohols, cyclic ethers, glycol ethers, etc. as necessary to deactivate and solubilize the catalyst, and then introduced into the upper part of the countercurrent washing tower. Ru.

There are no particular restrictions on the countercurrent washing tower used here, and various types of known shapes can be used, but a device that does not have means such as stirring and is exemplified in JP-A-58-210908 is stable. It can be used preferably because of its high performance. Regarding the concentration of the slurry introduced into the countercurrent cleaning tower, the ratio of the amount of slurry to the amount of washed propylene, the concentration of the slurry extracted, etc., the preferred range varies depending on the properties of the polypropylene, the shape of the countercurrent cleaning tower, etc., and cannot be specified. For example, JP-A-5
8-210908, JP-A No. 61-2708, etc. can be adopted.

What is important in the present invention is that the temperature of the washed propylene introduced from the lower part of the column is lower than that of the polypropylene slurry introduced above, and that the cleaning liquid extracted from the upper part of the column is heated so as not to fall below the temperature of the slurry introduced by more than 20°C. It is in.

The temperature of the washing propylene to be introduced is 1 to 80°C, preferably 5 to 4°C relative to the temperature of the polypropylene slurry.
Specifically, the temperature is 0°C lower than 0°C to 60°C.

If the temperature is higher than the temperature of the polypropylene slurry, the cleaning efficiency of the countercurrent washing tower will be reduced, and the efficiency of extracting the low-crystalline, low molecular weight polymer in the countercurrent washing tower will also be reduced. On the other hand, if the temperature is too low compared to the slurry temperature, the dissolved low-crystalline, low-molecular-weight polymer will precipitate and mix into the washed polypropylene extracted from below, which is undesirable.

Further, the temperature of the cleaning liquid is maintained at a temperature not lower than 20°C, preferably not lower than 10°C, with respect to the temperature of the polypropylene slurry introduced. Preferably, the temperature is maintained at -10°C to 20°C higher than the slurry to be introduced, specifically at 40°C to 80°C. Heating is performed by heating the cleaning liquid take-off line, including the area above the slurry introduction nozzle of the countercurrent cleaning tower, as necessary, using a heat source such as steam.

The cleaning liquid thus extracted is usually further heated to evaporate the propylene and separate it from the acidic polypropylene, so this heat treatment can be carried out without thermally making the polypropylene production process disadvantageous.

Effects By carrying out the method of the present invention, polypropylene can be efficiently purified without problems such as line blockage, which is extremely valuable industrially.

Example The present invention will be further explained with reference to Examples below.

In the Examples and Comparative Examples, the physical properties were 20/1 of the phenolic stabilizer to the copolymer.
0000 weight ratio, calcium stearate 10/10
000 weight ratio, lubricant 20/10000 weight ratio added 25
After granulation at 0℃, at 240℃ thickness 30μ width 25c+n
A T-die film was made and evaluated.

Each measurement was performed using melt flow index g/10m1n at 230°C with a load of 2.16Kg ASTM [+-1238-62T Haze (χ”) ASTM-1003-53
Prokeying (χ) 2 kg of two films stacked together
Young's modulus (Kg/mm) calculated as a percentage of the adhesion area after 24 hours at 50°C with a weight placed on it (2 x 220 mm)
Measured with Instron using a film of Ig/ci ASTM D882-
Impact (Kg, cm/mm) according to 64T Calculated from the impact energy when a 10 mm x 10 mm film is impacted with a spherical weight at 5°C and destroyed. Determined by visual inspection 22 soil 1Z Yu product 2 for 100g of copolymer powder
00ml of n-hexane at 30°C with stirring.
The powder was further washed with 100 ml of hexane, combined with the filtrate, the hexane was removed by evaporation, and the residue was further dried at 80° C. under a reduced pressure of 60 mmHg.

Example I A) Production of solid catalyst Internal volume 4 containing 9 kg of steel balls with a diameter of 12 + am! ! Prepare a vibrating mill equipped with four grinding pots. 300 g of magnesium chloride, 40 m of ethyl orthoacetate and 60 m of 1.1.2-dichloroethane in each pot under nitrogen atmosphere.
1 was added and the mixture was ground for 40 hours. The above pulverized material 3 was placed in a 50 J autoclave that was thoroughly dried and set in a nitrogen atmosphere.

Add 201 of titanium tetrachloride, stir at 80°C for 120 minutes, let it stand, remove the supernatant, add 35g of n-hebutane, and stir at 80°C for 120 minutes.
After stirring for 15 minutes at
After repeating this process several times, 202 ml of n-heptane was further added to form a solid catalyst slurry.

When a portion of the solid catalyst slurry was sampled, n-heptane was evaporated, and analyzed, it was found that the solid catalyst contained 1.62% by weight of Ti.

B) Polymerization reaction 15 kg of propylene was charged into a jacketed 100 J autoclave (autoclave A) which had been thoroughly dried, purged with nitrogen, and further purged with propylene, and then heated to 70°C. Meanwhile, in a 5j2 flask, add 2500ml of n-hebutane and 96ml of diethylaluminum chloride.
ml, 56 ml of methyl p-toluate, and 20 g of the above solid catalyst were added, and 10 ml of propylene was added with stirring at room temperature.
0g was charged. This catalyst slurry was charged into autoclave 8 as a solid catalyst at a rate of Lg/h, and while triethylaluminum was charged at a rate of 3ml/h, propylene was charged at a rate of 12Kg/h, and hydrogen and ethylene were charged at concentrations of 3.7χ and 2.0kg/h in the gas phase, respectively.
The slurry was charged so as to be maintained at 6χ, and the slurry was extracted from autoclave A at 12 kg/h into autoclave B. On the other hand, autoclave B contains 2.5 kg of n-hebutane.
, diethylene glycol monoisopropyl ether 10
m1. After adding 12 kg of propylene and raising the temperature to 55°C, the slurry was received from autoclave A. At the same time as the reception started, autoclave B contained 2.5 kg/h of n-heptane.
, diethylene glycol monoisopropyl ether 1
0m1/h was charged and the temperature was 52℃ from autoclave B.
Slurry is 14.5Kg/h and the inner diameter of the thin part is l Q
cm, the inner diameter of the thick part at the top is 30cm, the length of the thin part is 10ra, and the length of the thick part at the top is 2rn. Propylene 90χ,
A cleaning solution cooled to 20°C with a composition of 5x propane, 1x ethylene, and 4x n-hebutane was introduced at a rate of 40 kg/h,
The cleaning liquid was taken out at 44 kg/h from the top, and the slurry washed at 28°C was taken out at 26 kg/h from the bottom, and the taken out slurry was maintained at atmospheric pressure through a double pipe with an inner diameter of 374 inches and a length of 60 m. The double tube discharged into the cyclone was heated by IKg-G steam.

In this way, the powder taken out from the cyclone via the hopper contained 0.5x as volatile matter.

The obtained powder was further heated at 50°C and 50mmHg for 1
After drying for 0 hours, the weight was 11.2 kg. On the other hand, the upper part of the countercurrent washing tower and the washing liquid take-out line had a jacketed structure as shown in FIG. 1, and the washing liquid was heated by passing hot water therethrough. The flow meter and control valve were also heated by steam tracing. As a result, the upper part of the countercurrent washing tower was kept at 45°C and the cleaning liquid take-out line was kept at 55°C. The liquid composition of the cleaning solution is propylene 85w tχ, propane 4.2
wtχ, n-heptane 10-tχ, ethylene 0.8wt
χ, and by evaporating and removing these components, 0.6K
g/h of soluble polymer was obtained.

The polymerization reaction was carried out for 40 hours without any problem. The obtained powder was granulated and film-formed under the conditions described above, and its physical properties were measured.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the temperature of the cleaning liquid introduced was 55°C and the cleaning was performed at 52°C. There were no operational problems, but the physical properties were poor.

Comparative Example 2 When the upper part of the counter-current cleaning tower and the cleaning liquid take-out line were operated at 32°C and the cleaning liquid take-out line at 30°C without heating the upper part of the counter-current cleaning tower and the cleaning liquid take-out line, the flow meter reading changed significantly about 10 hours after the start of operation. It became difficult to control the flow rate, and after 12 hours, the amount of cleaning liquid drawn out decreased significantly, so the operation was discontinued. The physical properties of the random copolymers produced so far were good.

Example 2 As a solid catalyst, a highly active titanium trichloride catalyst (TAC-S-21) manufactured by Toho Titanium was used in toluene (vs. TAC-S).
-21,100g was washed three times with 500ml), and a catalyst consisting of 2.5g/h of solid catalyst and 20ml/h of diethylaluminium chloride was used.The charging rate of propylene to autoclave A was 8Kg/h, and to autoclave B. The procedure was the same as in Example 1, except that the slurry was withdrawn at a rate of 8 kg/h, the slurry was withdrawn from autoclave B at 10.5 kg/h, and the hydrogen concentration in the gas phase of autoclave A was 10.6χ. During 40 hours of operation. There were no problems (physical properties were also good. The powder was 1
It was obtained at a rate of 0.6 Kg/h, and the yield was 95.5 wtχ.

Comparative Example 3 When the upper part of the countercurrent cleaning tower and the cleaning liquid take-out line were operated at 32°C and the cleaning liquid take-out line at 30°C without heating the upper part of the countercurrent cleaning tower and the cleaning liquid take-out line, the flow meter reading changed significantly about 7 hours after the start of operation. So I stopped driving.

From the above Examples and Comparative Examples, extraction can be carried out efficiently by performing it at a low temperature (Table 1 of JP-A-48-93685).
It is also necessary to remove the portion extracted at a relatively high temperature (Example Autoclave B) for film physical properties, and that portion does not dissolve in low-temperature propylene. It can be assumed that operational problems such as blockage will occur. Therefore, the method of the present invention is considered to be extremely effective for improving the physical properties of products and eliminating operational troubles.

[Brief explanation of drawings]

The drawing (Figure 1) is a conceptual diagram of the equipment used to carry out the present invention, where A represents autoclave A, B represents autoclave B, C represents a countercurrent cleaning tower, D represents a double pipe, and E represents autoclave B. F indicates a cyclone, F indicates a hopper, a indicates cleaning liquid extraction, b indicates cleaning liquid introduction, C indicates medium vapor, and d indicates powder extraction. e is a flow meter and control valve f is a double pipe for heating. Patent applicant: Mitsui Toatsu Chemical Co., Ltd. Figure 1

Claims (1)

[Claims] A polypropylene slurry obtained by polymerization using a bulk polymerization method using propylene itself as a liquid medium is charged into the upper part of a countercurrent washing tower, washed propylene is introduced from the lower part of the tower, and the washed polypropylene is transferred from the lower part of the tower to the upper part of the tower. In a method for purifying polypropylene by extracting a washing liquid from the column, the temperature of the washing propylene introduced from the bottom of the column is lower than that of the polypropylene slurry introduced into the countercurrent washing column, and the temperature of the washing liquid extracted from the top of the column is lower than that of the slurry introduced. A method for purifying polypropylene, the method comprising heating the polypropylene so that the temperature does not drop below 20°C.